On This Day

Hydrogen

Discovered	State
1766	Gas
Atomic Mass	Density
1.008	0.08988 g/L

¹ ₁ H ₂

Electrons	Protons	Neutrons
1	1	0
Electronic Configuration
1s¹

Discovered By: Henry Cavendish
Appearance: colorless gas
Category: diatomic nonmetal
Melting Point: 13.99 K
Boiling Point: 20.271 K
Ox. State: -1, 1
Bonding Type: diatomic
Electronegativity: 2.2
Wiki Link: Source Link
Element Image: Image Link

Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.

Helium

Discovered	State
1895	Gas
Atomic Mass	Density
4.0026022	0.1786 g/L

⁴ ₂ He

Electrons	Protons	Neutrons
2	2	2
Electronic Configuration
1s²

Discovered By: Pierre Janssen
Appearance: colorless gas
Category: noble gas
Melting Point: 0.95 K
Boiling Point: 4.222 K
Ox. State:
Bonding Type: atomic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.

Lithium

Discovered	State
1817	Solid
Atomic Mass	Density
6.94	0.534 g/L

⁷ ₃ Li

Electrons	Protons	Neutrons
3	3	4
Electronic Configuration
[He] 2s¹

Discovered By: Johan August Arfwedson
Appearance: silvery-white
Category: alkali metal
Melting Point: 453.65 K
Boiling Point: 1615 K
Ox. State: 1
Bonding Type: metallic
Electronegativity: 0.98
Wiki Link: Source Link
Element Image: Image Link

Lithium (from Greek:λίθος lithos, "stone") is a chemical element with the symbol Li and atomic number 3. It is a soft, silver-white metal belonging to the alkali metal group of chemical elements. Under standard conditions it is the lightest metal and the least dense solid element.

Beryllium

Discovered	State
1798	Solid
Atomic Mass	Density
9.01218315	1.848 g/L

⁹ ₄ Be

Electrons	Protons	Neutrons
4	4	5
Electronic Configuration
[He] 2s²

Discovered By: Louis Nicolas Vauquelin
Appearance: white-gray
Category: alkaline earth metal
Melting Point: 1560 K
Boiling Point: 2743 K
Ox. State: 2
Bonding Type: metallic
Electronegativity: 1.57
Wiki Link: Source Link
Element Image: Image Link

Beryllium is a chemical element with symbol Be and atomic number 4. It is created through stellar nucleosynthesis and is a relatively rare element in the universe. It is a divalent element which occurs naturally only in combination with other elements in minerals.

Boron

Discovered	State
1807	Solid
Atomic Mass	Density
10.81	2.46 g/L

¹⁰ ₅ B

Electrons	Protons	Neutrons
5	5	5
Electronic Configuration
[He] 2s²2p¹

Discovered By: Joseph Louis Gay-Lussac
Appearance: black-brown
Category: metalloid
Melting Point: 2348 K
Boiling Point: 4273 K
Ox. State: 1, 2, 3
Bonding Type: covalent network
Electronegativity: 2.04
Wiki Link: Source Link
Element Image: Image Link

Boron is a metalloid chemical element with symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in both the Solar system and the Earth's crust. Boron is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals.

Carbon

Discovered	State
Ancient	Solid
Atomic Mass	Density
12.011	2.26 g/L

¹² ₆ C

Electrons	Protons	Neutrons
6	6	6
Electronic Configuration
[He] 2s²2p²

Discovered By: Ancient Egypt
Appearance: black
Category: polyatomic nonmetal
Melting Point: 3823 K
Boiling Point: 4300 K
Ox. State: -4, -3, -2, -1, 1, 2, 3, 4
Bonding Type: covalent network
Electronegativity: 2.55
Wiki Link: Source Link
Element Image: Image Link

Carbon (from Latin:carbo "coal") is a chemical element with symbol C and atomic number 6. On the periodic table, it is the first (row 2) of six elements in column (group) 14, which have in common the composition of their outer electron shell. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds.

Nitrogen

Discovered	State
1772	Gas
Atomic Mass	Density
14.0067	0.001251 g/L

¹⁴ ₇ N ₂

Electrons	Protons	Neutrons
7	7	7
Electronic Configuration
[He] 2s²2p³

Discovered By: Daniel Rutherford
Appearance: colorless gas
Category: diatomic nonmetal
Melting Point: 63 K
Boiling Point: 77 K
Ox. State: -3, -2, -1, 1, 2, 3, 4, 5
Bonding Type: diatomic
Electronegativity: 3.04
Wiki Link: Source Link
Element Image: Image Link

Nitrogen is a chemical element with symbol N and atomic number 7. It is the lightest pnictogen and at room temperature, it is a transparent, odorless diatomic gas. Nitrogen is a common element in the universe, estimated at about seventh in total abundance in the Milky Way and the Solar System.

Oxygen

Discovered	State
1774	Gas
Atomic Mass	Density
15.9994	1.429 g/L

¹⁶ ₈ O ₂

Electrons	Protons	Neutrons
8	8	8
Electronic Configuration
[He] 2s²2p⁴

Discovered By: Carl Wilhelm Scheele
Appearance: colorless gas
Category: diatomic nonmetal
Melting Point: 54.36 K
Boiling Point: 90.188 K
Ox. State: -2, -1, 1, 2
Bonding Type: diatomic
Electronegativity: 3.44
Wiki Link: Source Link
Element Image: Image Link

Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive nonmetal and oxidizing agent that readily forms compounds (notably oxides) with most elements. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium.

Fluorine

Discovered	State
1670	Gas
Atomic Mass	Density
18.998	1.696 g/L

¹⁹ ₉ F

Electrons	Protons	Neutrons
9	9	10
Electronic Configuration
[He] 2s²2p⁵

Discovered By: André-Marie Ampère
Appearance:
Category: diatomic nonmetal
Melting Point: 53.48 K
Boiling Point: 85.03 K
Ox. State: -1
Bonding Type: atomic
Electronegativity: 3.98
Wiki Link: Source Link
Element Image: Image Link

Fluorine is a chemical element with symbol F and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive:almost all other elements, including some noble gases, form compounds with fluorine.

Neon

Discovered	State
1898	Gas
Atomic Mass	Density
20.17976	0.9002 g/L

²⁰ ₁₀ Ne

Electrons	Protons	Neutrons
10	10	10
Electronic Configuration
[He] 2s²2p⁶

Discovered By: Morris Travers
Appearance: colorless gas
Category: noble gas
Melting Point: 24.56 K
Boiling Point: 27.104 K
Ox. State:
Bonding Type: atomic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Neon is a chemical element with symbol Ne and atomic number 10. It is in group 18 (noble gases) of the periodic table. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air.

Sodium

Discovered	State
1807	solid
Atomic Mass	Density
22.989	0.968 g/L

²³ ₁₁ Na

Electrons	Protons	Neutrons
11	11	12
Electronic Configuration
[Ne] 3s¹

Discovered By: Humphry Davy
Appearance: silvery white metallic
Category: alkali metal
Melting Point: 370.944 K
Boiling Point: 1156.09 K
Ox. State: -1, 1
Bonding Type: metallic
Electronegativity: 0.93
Wiki Link: Source Link
Element Image: Image Link

Sodium /ˈsoʊdiəm/ is a chemical element with symbol Na (from Ancient Greek Νάτριο) and atomic number 11. It is a soft, silver-white, highly reactive metal. In the Periodic table it is in column 1 (alkali metals), and shares with the other six elements in that column that it has a single electron in its outer shell, which it readily donates, creating a positively charged atom - a cation.

Magnesium

Discovered	State
1808	solid
Atomic Mass	Density
24.305	1.738 g/L

²⁴ ₁₂ Mg

Electrons	Protons	Neutrons
12	12	12
Electronic Configuration
[Ne] 3s²

Discovered By: Joseph Black
Appearance: shiny grey solid
Category: alkaline earth metal
Melting Point: 923 K
Boiling Point: 1363 K
Ox. State: 1, 2
Bonding Type: metallic
Electronegativity: 1.31
Wiki Link: Source Link
Element Image: Image Link

Magnesium is a chemical element with symbol Mg and atomic number 12. It is a shiny gray solid which bears a close physical resemblance to the other five elements in the second column (Group 2, or alkaline earth metals) of the periodic table:they each have the same electron configuration in their outer electron shell producing a similar crystal structure. Magnesium is the ninth most abundant element in the universe.

Aluminium

Discovered	State
Ancient	solid
Atomic Mass	Density
26.98153857	2.7 g/L

²⁷ ₁₃ Al

Electrons	Protons	Neutrons
13	13	14
Electronic Configuration
[Ne] 3s²3p¹

Discovered By: Humphry Davy
Appearance: silvery gray metallic
Category: post-transition metal
Melting Point: 933.47 K
Boiling Point: 2743 K
Ox. State: 1, 3
Bonding Type: metallic
Electronegativity: 1.61
Wiki Link: Source Link
Element Image: Image Link

Aluminium (or aluminum; see different endings) is a chemical element in the boron group with symbol Al and atomic number 13. It is a silvery-white, soft, nonmagnetic, ductile metal. Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal, in the Earth's crust.

Silicon

Discovered	State
1854	solid
Atomic Mass	Density
28.085	2.329 g/L

²⁸ ₁₄ Si

Electrons	Protons	Neutrons
14	14	14
Electronic Configuration
[Ne] 3s²3p²

Discovered By: Jöns Jacob Berzelius
Appearance: crystalline
Category: metalloid
Melting Point: 1687 K
Boiling Point: 3538 K
Ox. State: -4, -3, -2, -1, 1, 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.9
Wiki Link: Source Link
Element Image: Image Link

Silicon is a chemical element with symbol Si and atomic number 14. It is a tetravalent metalloid, more reactive than germanium, the metalloid directly below it in the table. Controversy about silicon's character dates to its discovery.

Phosphorus

Discovered	State
1669	solid
Atomic Mass	Density
30.9737619985	1.823 g/L

³¹ ₁₅ P

Electrons	Protons	Neutrons
15	15	16
Electronic Configuration
[Ne] 3s²3p³

Discovered By: Hennig Brand
Appearance: colourless
Category: polyatomic nonmetal
Melting Point: 317 K
Boiling Point: 554 K
Ox. State: -3, -2, -1, 1, 2, 3, 4, 5
Bonding Type: covalent network
Electronegativity: 2.19
Wiki Link: Source Link
Element Image: Image Link

Phosphorus is a chemical element with symbol P and atomic number 15. As an element, phosphorus exists in two major forms—white phosphorus and red phosphorus—but due to its high reactivity, phosphorus is never found as a free element on Earth. Instead phosphorus-containing minerals are almost always present in their maximally oxidised state, as inorganic phosphate rocks.

Sulfur

Discovered	State
Ancient	solid
Atomic Mass	Density
32.06	2.07 g/L

³² ₁₆ S

Electrons	Protons	Neutrons
16	16	16
Electronic Configuration
[Ne] 3s²3p⁴

Discovered By: Ancient china
Appearance: lemon yellow
Category: polyatomic nonmetal
Melting Point: 388.36 K
Boiling Point: 717.8 K
Ox. State: -2, -1, 1, 2, 3, 4, 5, 6
Bonding Type: covalent network
Electronegativity: 2.58
Wiki Link: Source Link
Element Image: Image Link

Sulfur or sulphur (see spelling differences) is a chemical element with symbol S and atomic number 16. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8.

Chlorine

Discovered	State
1774	Gas
Atomic Mass	Density
35.45	3.2 g/L

³⁵ ₁₇ Cl

Electrons	Protons	Neutrons
17	17	18
Electronic Configuration
[Ne] 3s²3p⁵

Discovered By: Carl Wilhelm Scheele
Appearance: pale yellow-green gas
Category: diatomic nonmetal
Melting Point: 171.6 K
Boiling Point: 239.11 K
Ox. State: -1, 1, 2, 3, 4, 5, 6, 7
Bonding Type: covalent network
Electronegativity: 3.16
Wiki Link: Source Link
Element Image: Image Link

Chlorine is a chemical element with symbol Cl and atomic number 17. It also has a relative atomic mass of 35.5. Chlorine is in the halogen group (17) and is the second lightest halogen following fluorine.

Argon

Discovered	State
1894	Gas
Atomic Mass	Density
39.9481	1.784 g/L

⁴⁰ ₁₈ Ar

Electrons	Protons	Neutrons
18	18	22
Electronic Configuration
[Ne] 3s²3p⁶

Discovered By: Lord Rayleigh
Appearance: colorless gas
Category: noble gas
Melting Point: 83.81 K
Boiling Point: 87.302 K
Ox. State:
Bonding Type: atomic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most common gas in the Earth's atmosphere, at 0.934% (9,340 ppmv), making it over twice as abundant as the next most common atmospheric gas, water vapor (which averages about 4000 ppmv, but varies greatly), and 23 times as abundant as the next most common non-condensing atmospheric gas, carbon dioxide (400 ppmv), and more than 500 times as abundant as the next most common noble gas, neon (18 ppmv).

Potassium

Discovered	State
1807	Solid
Atomic Mass	Density
39.09831	0.862 g/L

³⁹ ₁₉ K

Electrons	Protons	Neutrons
19	19	20
Electronic Configuration
[Ar] 4s¹

Discovered By: Humphry Davy
Appearance: silvery gray
Category: alkali metal
Melting Point: 336.7 K
Boiling Point: 1032 K
Ox. State: 1
Bonding Type: metallic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Potassium is a chemical element with symbol K (derived from Neo-Latin, kalium) and atomic number 19. It was first isolated from potash, the ashes of plants, from which its name is derived. In the Periodic table, potassium is one of seven elements in column (group) 1 (alkali metals):they all have a single valence electron in their outer electron shell, which they readily give up to create an atom with a positive charge - a cation, and combine with anions to form salts.

Calcium

Discovered	State
1808	Solid
Atomic Mass	Density
40.0784	1.55 g/L

⁴⁰ ₂₀ Ca

Electrons	Protons	Neutrons
20	20	20
Electronic Configuration
[Ar] 4s²

Discovered By: Humphry Davy
Appearance:
Category: alkaline earth metal
Melting Point: 1115 K
Boiling Point: 1757 K
Ox. State: 2
Bonding Type: metallic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft gray alkaline earth metal, fifth-most-abundant element by mass in the Earth's crust. The ion Ca2+ is also the fifth-most-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.

Scandium

Discovered	State
1876	Solid
Atomic Mass	Density
44.9559085	2.985 g/L

⁴⁵ ₂₁ Sc

Electrons	Protons	Neutrons
21	21	24
Electronic Configuration
[Ar] 3d¹4s²

Discovered By: Lars Fredrik Nilson
Appearance: silvery white
Category: transition metal
Melting Point: 1814 K
Boiling Point: 3109 K
Ox. State: 1, 2, 3
Bonding Type: metallic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Scandium is a chemical element with symbol Sc and atomic number 21. A silvery-white metallic d-block element, it has historically been sometimes classified as a rare earth element, together with yttrium and the lanthanoids. It was discovered in 1879 by spectral analysis of the minerals euxenite and gadolinite from Scandinavia.

Titanium

Discovered	State
1791	Solid
Atomic Mass	Density
44.9559085	4.506 g/L

⁴⁸ ₂₂ Ti

Electrons	Protons	Neutrons
22	22	26
Electronic Configuration
[Ar] 3d²4s²

Discovered By: William Gregor
Appearance: silvery grey
Category: transition metal
Melting Point: 1941 K
Boiling Point: 3560 K
Ox. State: -1, 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.54
Wiki Link: Source Link
Element Image: Image Link

Titanium is a chemical element with symbol Ti and atomic number 22. It is a lustrous transition metal with a silver color, low density and high strength. It is highly resistant to corrosion in sea water, aqua regia and chlorine.

Vanadium

Discovered	State
1803	Solid
Atomic Mass	Density
50.94151	6 g/L

⁵¹ ₂₃ V

Electrons	Protons	Neutrons
23	23	28
Electronic Configuration
[Ar] 3d³4s²

Discovered By: Andrés Manuel del Río
Appearance: blue-silver-grey metal
Category: transition metal
Melting Point: 2183 K
Boiling Point: 3680 K
Ox. State: -1, 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.63
Wiki Link: Source Link
Element Image: Image Link

Vanadium is a chemical element with symbol V and atomic number 23. It is a hard, silvery grey, ductile and malleable transition metal. The element is found only in chemically combined form in nature, but once isolated artificially, the formation of an oxide layer stabilizes the free metal somewhat against further oxidation.

Chromium

Discovered	State
1798	Solid
Atomic Mass	Density
51.99616	7.19 g/L

⁵² ₂₄ Cr

Electrons	Protons	Neutrons
24	24	28
Electronic Configuration
[Ar] 3d⁵4s¹

Discovered By: Louis Nicolas Vauquelin
Appearance: silvery metallic
Category: transition metal
Melting Point: 2180 K
Boiling Point: 2944 K
Ox. State: -2, -1, 1, 2, 3, 4, 5, 6
Bonding Type: metallic
Electronegativity: 1.63
Wiki Link: Source Link
Element Image: Image Link

Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard and brittle metal which takes a high polish, resists tarnishing, and has a high melting point.

Manganese

Discovered	State
1774	Solid
Atomic Mass	Density
54.9380443	7.21 g/L

⁵⁵ ₂₅ Mn

Electrons	Protons	Neutrons
25	25	30
Electronic Configuration
[Ar] 3d⁵4s²

Discovered By: Torbern Olof Bergman
Appearance: silvery metallic
Category: transition metal
Melting Point: 1519 K
Boiling Point: 2334 K
Ox. State: -2, -1, 1, 2, 3, 4, 5, 6
Bonding Type: metallic
Electronegativity: 1.55
Wiki Link: Source Link
Element Image: Image Link

Manganese is a chemical element with symbol Mn and atomic number 25. It is not found as a free element in nature; it is often found in combination with iron, and in many minerals. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.

Iron

Discovered	State
Ancient	Solid
Atomic Mass	Density
55.8452	7.874 g/L

⁵⁶ ₂₆ Fe

Electrons	Protons	Neutrons
26	26	30
Electronic Configuration
[Ar] 3d⁶4s²

Discovered By: 5000 BC
Appearance: lustrous metallic with a grayish tinge
Category: transition metal
Melting Point: 1811 K
Boiling Point: 3134 K
Ox. State: -2, -1, 1, 2, 3, 4, 5, 6
Bonding Type: metallic
Electronegativity: 1.83
Wiki Link: Source Link
Element Image: Image Link

Iron is a chemical element with symbol Fe (from Latin:ferrum) and atomic number 26. It is a metal in the first transition series. It is by mass the most common element on Earth, forming much of Earth's outer and inner core.

Cobalt

Discovered	State
Ancient	Solid
Atomic Mass	Density
58.9331944	8.9 g/L

⁵⁹ ₂₇ Co

Electrons	Protons	Neutrons
27	27	32
Electronic Configuration
[Ar] 3d⁷4s²

Discovered By: Georg Brandt
Appearance: hard lustrous gray metal
Category: transition metal
Melting Point: 1768 K
Boiling Point: 3200 K
Ox. State: -1, 1, 2, 3, 4, 5
Bonding Type: metallic
Electronegativity: 1.88
Wiki Link: Source Link
Element Image: Image Link

Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt in the Earth's crust is found only in chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal.

Nickel

Discovered	State
1751	Solid
Atomic Mass	Density
58.69344	8.908 g/L

⁵⁸ ₂₈ Ni

Electrons	Protons	Neutrons
28	28	30
Electronic Configuration
[Ar] 3d⁸4s²

Discovered By: Axel Fredrik Cronstedt
Appearance: lustrous, metallic, and silver with a gold tinge
Category: transition metal
Melting Point: 1728 K
Boiling Point: 3003 K
Ox. State: -1, 1, 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.91
Wiki Link: Source Link
Element Image: Image Link

Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile.

Copper

Discovered	State
Ancient	Solid
Atomic Mass	Density
63.5463	8.96 g/L

⁶⁴ ₂₉ Cu

Electrons	Protons	Neutrons
29	29	35
Electronic Configuration
[Ar] 3d¹⁰4s¹

Discovered By: Middle East
Appearance: red-orange metallic luster
Category: transition metal
Melting Point: 1357.77 K
Boiling Point: 2835 K
Ox. State: 1, 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.9
Wiki Link: Source Link
Element Image: Image Link

Copper is a chemical element with symbol Cu (from Latin:cuprum) and atomic number 29. It is a soft, malleable and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a reddish-orange color.

Zinc

Discovered	State
1746	Solid
Atomic Mass	Density
65.382	7.14 g/L

⁶⁵ ₃₀ Zn

Electrons	Protons	Neutrons
30	30	35
Electronic Configuration
[Ar] 3d¹⁰4s²

Discovered By: India
Appearance: silver-gray
Category: transition metal
Melting Point: 692.68 K
Boiling Point: 1180 K
Ox. State: 2
Bonding Type: metallic
Electronegativity: 1.65
Wiki Link: Source Link
Element Image: Image Link

Zinc, in commerce also spelter, is a chemical element with symbol Zn and atomic number 30. It is the first element of group 12 of the periodic table. In some respects zinc is chemically similar to magnesium:its ion is of similar size and its only common oxidation state is +2.

Gallium

Discovered	State
1875	Solid
Atomic Mass	Density
69.7231	5.91 g/L

⁷⁰ ₃₁ Ga

Electrons	Protons	Neutrons
31	31	39
Electronic Configuration
[Ar] 3d¹⁰4s²4p¹

Discovered By: Lecoq de Boisbaudran
Appearance: silver-white
Category: post-transition metal
Melting Point: 302.9146 K
Boiling Point: 2673 K
Ox. State: 1, 2, 3
Bonding Type: metallic
Electronegativity: 1.81
Wiki Link: Source Link
Element Image: Image Link

Gallium is a chemical element with symbol Ga and atomic number 31. Elemental gallium does not occur in free form in nature, but as the gallium(III) compounds that are in trace amounts in zinc ores and in bauxite. Gallium is a soft, silvery metal, and elemental gallium is a brittle solid at low temperatures, and melts at 29.76 °C (85.57 °F) (slightly above room temperature).

Germanium

Discovered	State
1886	Solid
Atomic Mass	Density
72.6308	5.323 g/L

⁷³ ₃₂ Ge

Electrons	Protons	Neutrons
32	32	41
Electronic Configuration
[Ar] 3d¹⁰4s²4p²

Discovered By: Lecoq de Boisbaudran
Appearance: grayish-white
Category: metalloid
Melting Point: 1211.4 K
Boiling Point: 3106 K
Ox. State: -4, 1, 2, 3, 4
Bonding Type: metallic
Electronegativity: 2.01
Wiki Link: Source Link
Element Image: Image Link

Germanium is a chemical element with symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. Purified germanium is a semiconductor, with an appearance most similar to elemental silicon.

Arsenic

Discovered	State
Ancient	Solid
Atomic Mass	Density
74.9215956	5.727 g/L

⁷⁵ ₃₃ As

Electrons	Protons	Neutrons
33	33	42
Electronic Configuration
[Ar] 3d¹⁰4s²4p³

Discovered By: Bronze Age
Appearance: metallic grey
Category: metalloid
Melting Point: 1090 K
Boiling Point: 887 K
Ox. State: -3, 2, 3, 5
Bonding Type: metallic
Electronegativity: 2.18
Wiki Link: Source Link
Element Image: Image Link

Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. Arsenic is a metalloid.

Selenium

Discovered	State
1817	Solid
Atomic Mass	Density
78.9718	4.81 g/L

⁷⁹ ₃₄ Se

Electrons	Protons	Neutrons
34	34	45
Electronic Configuration
[Ar] 3d¹⁰4s²4p⁴

Discovered By: Jöns Jakob Berzelius
Appearance: black, red
Category: polyatomic nonmetal
Melting Point: 494 K
Boiling Point: 958 K
Ox. State: -2, 2, 4, 6
Bonding Type: metallic
Electronegativity: 2.55
Wiki Link: Source Link
Element Image: Image Link

Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between those of its periodic table column-adjacent chalcogen elements sulfur and tellurium. It rarely occurs in its elemental state in nature, or as pure ore compounds.

Bromine

Discovered	State
1826	Liquid
Atomic Mass	Density
79.904	23.1028 g/L

⁸⁰ ₃₅ Br ₂

Electrons	Protons	Neutrons
35	35	45
Electronic Configuration
[Ar] 3d¹⁰4s²4p⁵

Discovered By: Antoine Jérôme Balard
Appearance:
Category: diatomic nonmetal
Melting Point: 265.8 K
Boiling Point: 332 K
Ox. State: -1, 1, 3, 4, 5, 7
Bonding Type: covalent network
Electronegativity: 2.96
Wiki Link: Source Link
Element Image: Image Link

Bromine (from Ancient Greek:βρῶμος, brómos, meaning "stench") is a chemical element with symbol Br, and atomic number 35. It is a halogen. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826.

Krypton

Discovered	State
1898	Gas
Atomic Mass	Density
83.7982	3.749 g/L

⁸⁴ ₃₆ Kr

Electrons	Protons	Neutrons
36	36	48
Electronic Configuration
[Ar] 3d¹⁰4s²4p⁶

Discovered By: William Ramsay
Appearance: colorless gas
Category: noble gas
Melting Point: 115.78 K
Boiling Point: 119.93 K
Ox. State: 2
Bonding Type: atomic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Krypton (from Greek:κρυπτός kryptos "the hidden one") is a chemical element with symbol Kr and atomic number 36. It is a member of group 18 (noble gases) elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquefied air, and is often used with other rare gases in fluorescent lamps.

Rubidium

Discovered	State
1861	Solid
Atomic Mass	Density
85.46783	1.532 g/L

⁸⁵ ₃₇ Rb

Electrons	Protons	Neutrons
37	37	48
Electronic Configuration
[Kr] 5s¹

Discovered By: Robert Bunsen
Appearance: grey white
Category: alkali metal
Melting Point: 312.45 K
Boiling Point: 961 K
Ox. State: 1
Bonding Type: metallic
Electronegativity: 0.82
Wiki Link: Source Link
Element Image: Image Link

Rubidium is a chemical element with symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group, with an atomic mass of 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other alkali metals, such as very rapid oxidation in air.

Strontium

Discovered	State
1790	Solid
Atomic Mass	Density
87.621	2.64 g/L

⁸⁸ ₃₈ Sr

Electrons	Protons	Neutrons
38	38	50
Electronic Configuration
[Kr] 5s²

Discovered By: William Cruickshank (chemist)
Appearance:
Category: alkaline earth metal
Melting Point: 1050 K
Boiling Point: 1650 K
Ox. State: 2
Bonding Type: metallic
Electronegativity: 0.95
Wiki Link: Source Link
Element Image: Image Link

Strontium is a chemical element with symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when it is exposed to air.

Yttrium

Discovered	State
1794	Solid
Atomic Mass	Density
88.905842	4.472 g/L

⁸⁹ ₃₉ Y

Electrons	Protons	Neutrons
39	39	50
Electronic Configuration
[Kr] 4d¹5s²

Discovered By: Johan Gadolin
Appearance: silvery white
Category: transition metal
Melting Point: 1799 K
Boiling Point: 3203 K
Ox. State: 1, 2, 3
Bonding Type: metallic
Electronegativity: 1.22
Wiki Link: Source Link
Element Image: Image Link

Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is never found in nature as a free element.

Zirconium

Discovered	State
1789	Solid
Atomic Mass	Density
91.2242	6.52 g/L

⁹¹ ₄₀ Zr

Electrons	Protons	Neutrons
40	40	51
Electronic Configuration
[Kr] 4d²5s²

Discovered By: Martin Heinrich Klaproth
Appearance: silvery white
Category: transition metal
Melting Point: 2128 K
Boiling Point: 4650 K
Ox. State: 1, 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.33
Wiki Link: Source Link
Element Image: Image Link

Zirconium is a chemical element with symbol Zr and atomic number 40. The name of zirconium is taken from the name of the mineral zircon, the most important source of zirconium. The word zircon comes from the Persian word zargun زرگون, meaning "gold-colored".

Niobium

Discovered	State
1801	Solid
Atomic Mass	Density
92.906372	8.57 g/L

⁹³ ₄₁ Nb

Electrons	Protons	Neutrons
41	41	52
Electronic Configuration
[Kr] 4d⁴5s¹

Discovered By: Charles Hatchett
Appearance: gray metallic, bluish when oxidized
Category: transition metal
Melting Point: 2750 K
Boiling Point: 5017 K
Ox. State: -1, 2, 3, 4, 5
Bonding Type: metallic
Electronegativity: 1.6
Wiki Link: Source Link
Element Image: Image Link

Niobium, formerly columbium, is a chemical element with symbol Nb (formerly Cb) and atomic number 41. It is a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite. The name comes from Greek mythology:Niobe, daughter of Tantalus since it is so similar to tantalum.

Molybdenum

Discovered	State
1778	Solid
Atomic Mass	Density
95.951	10.28 g/L

⁹⁶ ₄₂ Mo

Electrons	Protons	Neutrons
42	42	54
Electronic Configuration
[Kr] 4d⁵5s¹

Discovered By: Carl Wilhelm Scheele
Appearance: gray metallic,
Category: transition metal
Melting Point: 2896 K
Boiling Point: 4912 K
Ox. State: -2, -1, 1, 2, 3, 4, 5, 6
Bonding Type: metallic
Electronegativity: 2.16
Wiki Link: Source Link
Element Image: Image Link

Molybdenum is a chemical element with symbol Mo and atomic number 42. The name is from Neo-Latin molybdaenum, from Ancient Greek Μόλυβδος molybdos, meaning lead, since its ores were confused with lead ores. Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm Scheele.

Technetium

Discovered	State
1937	Solid
Atomic Mass	Density
98	11 g/L

⁹⁸ ₄₃ Tc

Electrons	Protons	Neutrons
43	43	55
Electronic Configuration
[Kr] 4d⁵5s²

Discovered By: Emilio Segrè
Appearance: shiny gray metal
Category: transition metal
Melting Point: 2430 K
Boiling Point: 4538 K
Ox. State: -3, -1, 1, 2, 3, 4, 5, 6, 7
Bonding Type: metallic
Electronegativity: 1.9
Wiki Link: Source Link
Element Image: Image Link

Technetium (/tɛkˈniːʃiəm/) is a chemical element with symbol Tc and atomic number 43. It is the element with the lowest atomic number in the periodic table that has no stable isotopes:every form of it is radioactive. Nearly all technetium is produced synthetically, and only minute amounts are found in nature.

Ruthenium

Discovered	State
1827	Solid
Atomic Mass	Density
101.072	12.37 g/L

¹⁰¹ ₄₄ Ru

Electrons	Protons	Neutrons
44	44	57
Electronic Configuration
[Kr] 4d⁷5s¹

Discovered By: Karl Ernst Claus
Appearance: silvery white metallic
Category: transition metal
Melting Point: 2607 K
Boiling Point: 4423 K
Ox. State: -2, 1, 2, 3, 4, 5, 6, 7, 8
Bonding Type: metallic
Electronegativity: 2.2
Wiki Link: Source Link
Element Image: Image Link

Ruthenium is a chemical element with symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemicals.

Rhodium

Discovered	State
1803	Solid
Atomic Mass	Density
101.072	12.41 g/L

¹⁰³ ₄₅ Rh

Electrons	Protons	Neutrons
45	45	58
Electronic Configuration
[Kr] 4d⁸5s¹

Discovered By: William Hyde Wollaston
Appearance: silvery white metallic
Category: transition metal
Melting Point: 2237 K
Boiling Point: 3968 K
Ox. State: -1, 1, 2, 3, 4, 5, 6
Bonding Type: metallic
Electronegativity: 2.28
Wiki Link: Source Link
Element Image: Image Link

Rhodium is a chemical element with symbol Rh and atomic number 45. It is a rare, silvery-white, hard, and chemically inert transition metal. It is a member of the platinum group.

Palladium

Discovered	State
1803	Solid
Atomic Mass	Density
106.421	12.023 g/L

¹⁰⁶ ₄₆ Pd

Electrons	Protons	Neutrons
46	46	60
Electronic Configuration
[Kr] 4d¹⁰

Discovered By: William Hyde Wollaston
Appearance: silvery white
Category: transition metal
Melting Point: 1828.05 K
Boiling Point: 3236 K
Ox. State: 2, 4
Bonding Type: metallic
Electronegativity: 2.2
Wiki Link: Source Link
Element Image: Image Link

Palladium is a chemical element with symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas.

Silver

Discovered	State
Ancient	Solid
Atomic Mass	Density
107.86822	10.49 g/L

¹⁰⁸ ₄₇ Ag

Electrons	Protons	Neutrons
47	47	61
Electronic Configuration
[Kr] 4d¹⁰5s¹

Discovered By: unknown, before 5000 BC
Appearance: lustrous white metal
Category: transition metal
Melting Point: 1234.93 K
Boiling Point: 2435 K
Ox. State: 1, 2, 3
Bonding Type: metallic
Electronegativity: 1.93
Wiki Link: Source Link
Element Image: Image Link

Silver is a chemical element with symbol Ag (Greek:άργυρος árguros, Latin:argentum, both from the Indo-European root *h₂erǵ- for "grey" or "shining") and atomic number 47. A soft, white, lustrous transition metal, it possesses the highest electrical conductivity, thermal conductivity and reflectivity of any metal. The metal occurs naturally in its pure, free form (native silver), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite.

Cadmium

Discovered	State
1817	Solid
Atomic Mass	Density
112.4144	8.65 g/L

¹¹² ₄₈ Cd

Electrons	Protons	Neutrons
48	48	64
Electronic Configuration
[Kr] 4d¹⁰5s²

Discovered By: Karl Samuel Leberecht Hermann
Appearance: silvery bluish-gray metallic
Category: transition metal
Melting Point: 594.22 K
Boiling Point: 1040 K
Ox. State: 2
Bonding Type: metallic
Electronegativity: 1.69
Wiki Link: Source Link
Element Image: Image Link

Cadmium is a chemical element with symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it prefers oxidation state +2 in most of its compounds and like mercury it shows a low melting point compared to transition metals.

Indium

Discovered	State
1863	Solid
Atomic Mass	Density
114.8181	7.31 g/L

¹¹⁵ ₄₉ In

Electrons	Protons	Neutrons
49	49	66
Electronic Configuration
[Kr] 4d¹⁰5s²5p¹

Discovered By: Ferdinand Reich
Appearance: silvery lustrous gray
Category: post-transition metal
Melting Point: 429.7485 K
Boiling Point: 2345 K
Ox. State: 1, 2, 3
Bonding Type: metallic
Electronegativity: 1.78
Wiki Link: Source Link
Element Image: Image Link

Indium is a chemical element with symbol In and atomic number 49. It is a post-transition metallic element that is rare in Earth's crust. The metal is very soft, malleable and easily fusible, with a melting point higher than sodium, but lower than lithium or tin.

Tin

Discovered	State
Ancient	Solid
Atomic Mass	Density
118.7107	7.365 g/L

¹¹⁹ ₅₀ Sn

Electrons	Protons	Neutrons
50	50	69
Electronic Configuration
[Kr] 4d¹⁰5s²5p²

Discovered By: unknown, before 3500 BC
Appearance: silvery-white (beta, β) or gray (alpha, α)
Category: post-transition metal
Melting Point: 505.08 K
Boiling Point: 2875 K
Ox. State: -4, 2, 4
Bonding Type: metallic
Electronegativity: 1.96
Wiki Link: Source Link
Element Image: Image Link

Tin is a chemical element with the symbol Sn (for Latin:stannum) and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows a chemical similarity to both neighboring group-14 elements, germanium and lead, and has two possible oxidation states, +2 and the slightly more stable +4.

Antimony

Discovered	State
Ancient	Solid
Atomic Mass	Density
121.7601	6.697 g/L

¹²² ₅₁ Sb

Electrons	Protons	Neutrons
51	51	71
Electronic Configuration
[Kr] 4d¹⁰5s²5p³

Discovered By: unknown, before 3000 BC
Appearance: silvery lustrous gray
Category: metalloid
Melting Point: 903.78 K
Boiling Point: 1908 K
Ox. State: -3, 3, 5
Bonding Type: metallic
Electronegativity: 2.05
Wiki Link: Source Link
Element Image: Image Link

Antimony is a chemical element with symbol Sb (from Latin:stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient times and were used for cosmetics; metallic antimony was also known, but it was erroneously identified as lead upon its discovery.

Tellurium

Discovered	State
1782	Solid
Atomic Mass	Density
127.603	6.24 g/L

¹²⁸ ₅₂ Te

Electrons	Protons	Neutrons
52	52	76
Electronic Configuration
[Kr] 4d¹⁰5s²5p⁴

Discovered By: Franz-Joseph Müller von Reichenstein
Appearance:
Category: metalloid
Melting Point: 722.66 K
Boiling Point: 1261 K
Ox. State: -2, 2, 4, 5, 6
Bonding Type: metallic
Electronegativity: 2.1
Wiki Link: Source Link
Element Image: Image Link

Tellurium is a chemical element with symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur.

Iodine

Discovered	State
1811	Solid
Atomic Mass	Density
126.904473	4.933 g/L

¹²⁷ ₅₃ I ₂

Electrons	Protons	Neutrons
53	53	74
Electronic Configuration
[Kr] 4d¹⁰5s²5p⁵

Discovered By: Bernard Courtois
Appearance: lustrous metallic gray, violet as a gas
Category: halogen
Melting Point: 386.85 K
Boiling Point: 457.4 K
Ox. State: -1, 1, 3, 5, 7
Bonding Type: metallic
Electronegativity: 2.66
Wiki Link: Source Link
Element Image: Image Link

Iodine is a chemical element with symbol I and atomic number 53. The name is from Greek ἰοειδής ioeidēs, meaning violet or purple, due to the color of iodine vapor. Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers.

Xenon

Discovered	State
1898	Gas
Atomic Mass	Density
131.2936	5.894 g/L

¹³¹ ₅₄ Xe

Electrons	Protons	Neutrons
54	54	77
Electronic Configuration
[Kr] 4d¹⁰5s²5p⁶

Discovered By: William Ramsay
Appearance: colorless gas
Category: noble gas
Melting Point: 161.4 K
Boiling Point: 165.051 K
Ox. State: 2, 4, 6, 8
Bonding Type: metallic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, dense, odorless noble gas, that occurs in the Earth's atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.

Caesium

Discovered	State
1860	Solid
Atomic Mass	Density
132.905451966	1.93 g/L

¹³³ ₅₅ Cs

Electrons	Protons	Neutrons
55	55	78
Electronic Configuration
[Xe] 6s¹

Discovered By: Robert Bunsen
Appearance: silvery gold
Category: alkali metal
Melting Point: 301.7 K
Boiling Point: 944 K
Ox. State: 1
Bonding Type: metallic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Caesium or cesium is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F), which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium is an alkali metal and has physical and chemical properties similar to those of rubidium and potassium.

Barium

Discovered	State
1808	Solid
Atomic Mass	Density
137.3277	3.51 g/L

¹³⁷ ₅₆ Ba

Electrons	Protons	Neutrons
56	56	81
Electronic Configuration
[Xe] 6s²

Discovered By: Carl Wilhelm Scheele
Appearance: silvery gold
Category: alkaline earth metal
Melting Point: 1000 K
Boiling Point: 2118 K
Ox. State: 2
Bonding Type: metallic
Electronegativity: 0.89
Wiki Link: Source Link
Element Image: Image Link

Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Because of its high chemical reactivity barium is never found in nature as a free element.

Lanthanum

Discovered	State
1839	Solid
Atomic Mass	Density
138.905477	6.162 g/L

¹³⁹ ₅₇ La

Electrons	Protons	Neutrons
57	57	82
Electronic Configuration
[Xe] 5d¹6s²

Discovered By: Carl Gustaf Mosander
Appearance: silvery white
Category: lanthanide
Melting Point: 1193 K
Boiling Point: 3737 K
Ox. State: 2, 3
Bonding Type: metallic
Electronegativity: 1.1
Wiki Link: Source Link
Element Image: Image Link

Lanthanum is a soft, ductile, silvery-white metallic chemical element with symbol La and atomic number 57. It tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. It gave its name to the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table:it is also sometimes considered the first element of the 6th-period transition metals.

Cerium

Discovered	State
1803	Solid
Atomic Mass	Density
140.1161	6.77 g/L

¹⁴⁰ ₅₈ Ce

Electrons	Protons	Neutrons
58	58	82
Electronic Configuration
[Xe] 4f¹5d¹6s²

Discovered By: Martin Heinrich Klaproth
Appearance: silvery white
Category: lanthanide
Melting Point: 1068 K
Boiling Point: 3716 K
Ox. State: 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.12
Wiki Link: Source Link
Element Image: Image Link

Cerium is a chemical element with symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet Ceres (itself named after the Roman goddess of agriculture).

Praseodymium

Discovered	State
1885	Solid
Atomic Mass	Density
140.907662	6.77 g/L

¹⁴¹ ₅₉ Pr

Electrons	Protons	Neutrons
59	59	82
Electronic Configuration
[Xe] 4f³6s²

Discovered By: Carl Auer von Welsbach
Appearance: grayish white
Category: lanthanide
Melting Point: 1208 K
Boiling Point: 3403 K
Ox. State: 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.13
Wiki Link: Source Link
Element Image: Image Link

Praseodymium is a chemical element with symbol Pr and atomic number 59. Praseodymium is a soft, silvery, malleable and ductile metal in the lanthanide group. It is valued for its magnetic, electrical, chemical, and optical properties.

Neodymium

Discovered	State
1885	Solid
Atomic Mass	Density
144.2423	7.01 g/L

¹⁴⁴ ₆₀ Nd

Electrons	Protons	Neutrons
60	60	84
Electronic Configuration
[Xe] 4f⁴6s²

Discovered By: Carl Auer von Welsbach
Appearance: silvery white
Category: lanthanide
Melting Point: 1297 K
Boiling Point: 3347 K
Ox. State: 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.14
Wiki Link: Source Link
Element Image: Image Link

Neodymium is a chemical element with symbol Nd and atomic number 60. It is a soft silvery metal that tarnishes in air. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach.

Promethium

Discovered	State
1947	Solid
Atomic Mass	Density
145	7.26 g/L

¹⁴⁵ ₆₁ Pm

Electrons	Protons	Neutrons
61	61	84
Electronic Configuration
[Xe] 4f⁵6s²

Discovered By: Chien Shiung Wu
Appearance: silvery white
Category: lanthanide
Melting Point: 1315 K
Boiling Point: 3273 K
Ox. State: 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.13
Wiki Link: Source Link
Element Image: Image Link

Promethium, originally prometheum, is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. Chemically, promethium is a lanthanide, which forms salts when combined with other elements.

Samarium

Discovered	State
1853	Solid
Atomic Mass	Density
150.362	7.52 g/L

¹⁵⁰ ₆₂ Sm

Electrons	Protons	Neutrons
62	62	88
Electronic Configuration
[Xe] 4f⁶6s²

Discovered By: Lecoq de Boisbaudran
Appearance: silvery white
Category: lanthanide
Melting Point: 1345 K
Boiling Point: 2173 K
Ox. State: 2, 3
Bonding Type: metallic
Electronegativity: 1.17
Wiki Link: Source Link
Element Image: Image Link

Samarium is a chemical element with symbol Sm and atomic number 62. It is a moderately hard silvery metal that readily oxidizes in air. Being a typical member of the lanthanide series, samarium usually assumes the oxidation state +3.

Europium

Discovered	State
1901	Solid
Atomic Mass	Density
151.9641	5.264 g/L

¹⁵² ₆₃ Eu

Electrons	Protons	Neutrons
63	63	89
Electronic Configuration
[Xe] 4f⁷6s²

Discovered By: Eugène-Anatole Demarçay
Appearance: silvery white
Category: lanthanide
Melting Point: 1099 K
Boiling Point: 1802 K
Ox. State: 2, 3
Bonding Type: metallic
Electronegativity: 1.2
Wiki Link: Source Link
Element Image: Image Link

Europium is a chemical element with symbol Eu and atomic number 63. It was isolated in 1901 and is named after the continent of Europe. It is a moderately hard, silvery metal which readily oxidizes in air and water.

Gadolinium

Discovered	State
1880	Solid
Atomic Mass	Density
157.253	7.9 g/L

¹⁵⁷ ₆₄ Gd

Electrons	Protons	Neutrons
64	64	93
Electronic Configuration
[Xe] 4f⁷5d¹6s²

Discovered By: Jean Charles Galissard de Marignac
Appearance: silvery white
Category: lanthanide
Melting Point: 1585 K
Boiling Point: 3273 K
Ox. State: 1, 2, 3
Bonding Type: metallic
Electronegativity: 1.2
Wiki Link: Source Link
Element Image: Image Link

Gadolinium is a chemical element with symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. It is found in nature only in combined (salt) form.

Terbium

Discovered	State
1843	Solid
Atomic Mass	Density
158.925352	8.23 g/L

¹⁵⁹ ₆₅ Tb

Electrons	Protons	Neutrons
65	65	94
Electronic Configuration
[Xe] 4f⁹6s²

Discovered By: Carl Gustaf Mosander
Appearance: silvery white
Category: lanthanide
Melting Point: 1629 K
Boiling Point: 3396 K
Ox. State: 1, 3, 4
Bonding Type: metallic
Electronegativity: 1.2
Wiki Link: Source Link
Element Image: Image Link

Terbium is a chemical element with symbol Tb and atomic number 65. It is a silvery-white rare earth metal that is malleable, ductile and soft enough to be cut with a knife. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite.

Dysprosium

Discovered	State
1886	Solid
Atomic Mass	Density
162.5001	8.54 g/L

¹⁶³ ₆₆ Dy

Electrons	Protons	Neutrons
66	66	97
Electronic Configuration
[Xe] 4f⁹6s²

Discovered By: Lecoq de Boisbaudran
Appearance: silvery white
Category: lanthanide
Melting Point: 1680 K
Boiling Point: 2840 K
Ox. State: 2, 3
Bonding Type: metallic
Electronegativity: 1.22
Wiki Link: Source Link
Element Image: Image Link

Dysprosium is a chemical element with the symbol Dy and atomic number 66. It is a rare earth element with a metallic silver luster. Dysprosium is never found in nature as a free element, though it is found in various minerals, such as xenotime.

Holmium

Discovered	State
1878	Solid
Atomic Mass	Density
164.930332	8.79 g/L

¹⁶⁵ ₆₇ Ho

Electrons	Protons	Neutrons
67	67	98
Electronic Configuration
[Xe] 4f¹¹6s²

Discovered By: Marc Delafontaine
Appearance: silvery white
Category: lanthanide
Melting Point: 1734 K
Boiling Point: 2873 K
Ox. State: 2, 3
Bonding Type: metallic
Electronegativity: 1.23
Wiki Link: Source Link
Element Image: Image Link

Holmium is a chemical element with symbol Ho and atomic number 67. Part of the lanthanide series, holmium is a rare earth element. Holmium was discovered by Swedish chemist Per Theodor Cleve.

Erbium

Discovered	State
1842	Solid
Atomic Mass	Density
167.2593	9.066 g/L

¹⁶⁷ ₆₈ Er

Electrons	Protons	Neutrons
68	68	99
Electronic Configuration
[Xe] 4f¹²6s²

Discovered By: Carl Gustaf Mosander
Appearance: silvery white
Category: lanthanide
Melting Point: 1802 K
Boiling Point: 3141 K
Ox. State: 3
Bonding Type: metallic
Electronegativity: 1.24
Wiki Link: Source Link
Element Image: Image Link

Erbium is a chemical element in the lanthanide series, with symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements on Earth. As such, it is a rare earth element which is associated with several other rare elements in the mineral gadolinite from Ytterby in Sweden, where yttrium, ytterbium, and terbium were discovered.

Thulium

Discovered	State
1879	Solid
Atomic Mass	Density
168.934222	9.32 g/L

¹⁶⁹ ₆₉ Tm

Electrons	Protons	Neutrons
69	69	100
Electronic Configuration
[Xe] 4f¹³6s²

Discovered By: Per Teodor Cleve
Appearance: silvery gray
Category: lanthanide
Melting Point: 1818 K
Boiling Point: 2223 K
Ox. State: 2, 3
Bonding Type: metallic
Electronegativity: 1.25
Wiki Link: Source Link
Element Image: Image Link

Thulium is a chemical element with symbol Tm and atomic number 69. It is the thirteenth and antepenultimate (third-last) element in the lanthanide series. Like the other lanthanides, the most common oxidation state is +3, seen in its oxide, halides and other compounds.

Ytterbium

Discovered	State
1878	Solid
Atomic Mass	Density
173.0451	6.9 g/L

¹⁷³ ₇₀ Yb

Electrons	Protons	Neutrons
70	70	103
Electronic Configuration
[Xe] 4f¹⁴6s²

Discovered By: Jean Charles Galissard de Marignac
Appearance: silvery gray
Category: lanthanide
Melting Point: 1097 K
Boiling Point: 1469 K
Ox. State: 2, 3
Bonding Type: metallic
Electronegativity: 1.1
Wiki Link: Source Link
Element Image: Image Link

Ytterbium is a chemical element with symbol Yb and atomic number 70. It is the fourteenth and penultimate element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. However, like the other lanthanides, its most common oxidation state is +3, seen in its oxide, halides and other compounds.

Lutetium

Discovered	State
1907	Solid
Atomic Mass	Density
174.96681	9.841 g/L

¹⁷⁵ ₇₁ Lu

Electrons	Protons	Neutrons
71	71	104
Electronic Configuration
[Xe] 4f¹⁴5d¹6s²

Discovered By: Georges Urbain
Appearance: silvery white
Category: lanthanide
Melting Point: 1925 K
Boiling Point: 3675 K
Ox. State: 3
Bonding Type: metallic
Electronegativity: 1.27
Wiki Link: Source Link
Element Image: Image Link

Lutetium is a chemical element with symbol Lu and atomic number 71. It is a silvery white metal, which resists corrosion in dry, but not in moist air. It is considered the first element of the 6th-period transition metals and the last element in the lanthanide series, and is traditionally counted among the rare earths.

Hafnium

Discovered	State
1923	Solid
Atomic Mass	Density
178.492	13.31 g/L

¹⁷⁸ ₇₂ Hf

Electrons	Protons	Neutrons
72	72	106
Electronic Configuration
[Xe] 4f¹⁴5d²6s²

Discovered By: Dirk Coster
Appearance: steel gray
Category: transition metal
Melting Point: 2506 K
Boiling Point: 4876 K
Ox. State: 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Hafnium is a chemical element with symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, making it the penultimate stable element to be discovered (rhenium was identified two years later).

Tantalum

Discovered	State
1802	Solid
Atomic Mass	Density
180.947882	16.69 g/L

¹⁸¹ ₇₃ Ta

Electrons	Protons	Neutrons
73	73	108
Electronic Configuration
[Xe] 4f¹⁴5d³6s²

Discovered By: Anders Gustaf Ekeberg
Appearance: gray blue
Category: transition metal
Melting Point: 3290 K
Boiling Point: 5731 K
Ox. State: 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.5
Wiki Link: Source Link
Element Image: Image Link

Tantalum is a chemical element with symbol Ta and atomic number 73. Previously known as tantalium, its name comes from Tantalus, an antihero from Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion-resistant.

Tungsten

Discovered	State
1783	Solid
Atomic Mass	Density
183.841	19.25 g/L

¹⁸⁴ ₇₄ W

Electrons	Protons	Neutrons
74	74	110
Electronic Configuration
[Xe] 4f¹⁴5d⁴6s²

Discovered By: Carl Wilhelm Scheele
Appearance: grayish white, lustrous
Category: transition metal
Melting Point: 3695 K
Boiling Point: 6203 K
Ox. State: -2, -1, 1, 2, 3, 4, 5, 6
Bonding Type: metallic
Electronegativity: 2.36
Wiki Link: Source Link
Element Image: Image Link

Tungsten, also known as wolfram, is a chemical element with symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten, which directly translates to heavy stone. Its name in Swedish is volfram, however, in order to distinguish it from scheelite, which in Swedish is alternatively named tungsten.

Rhenium

Discovered	State
1925	Solid
Atomic Mass	Density
186.2071	21.02 g/L

¹⁸⁶ ₇₅ Re

Electrons	Protons	Neutrons
75	75	111
Electronic Configuration
[Xe] 4f¹⁴5d⁵6s²

Discovered By: Masataka Ogawa
Appearance: silvery-grayish
Category: transition metal
Melting Point: 3459 K
Boiling Point: 5869 K
Ox. State: -3, -1, 1, 2, 3, 4, 5, 6, 7
Bonding Type: metallic
Electronegativity: 1.9
Wiki Link: Source Link
Element Image: Image Link

Rhenium is a chemical element with symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust.

Osmium

Discovered	State
1803	Solid
Atomic Mass	Density
190.233	22.59 g/L

¹⁸⁷ ₇₆ Os

Electrons	Protons	Neutrons
76	76	111
Electronic Configuration
[Xe] 4f¹⁴5d⁶6s²

Discovered By: Smithson Tennant
Appearance: silvery, blue cast
Category: transition metal
Melting Point: 3306 K
Boiling Point: 5285 K
Ox. State: -2, -1, 1, 2, 3, 4, 5, 6, 7, 8
Bonding Type: metallic
Electronegativity: 2.2
Wiki Link: Source Link
Element Image: Image Link

Osmium (from Greek osme (ὀσμή) meaning "smell") is a chemical element with symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element, with a density of 22.59 g/cm3.

Iridium

Discovered	State
1803	Solid
Atomic Mass	Density
192.2173	22.56 g/L

¹⁹² ₇₇ Ir

Electrons	Protons	Neutrons
77	77	115
Electronic Configuration
[Xe] 4f¹⁴5d⁷6s²

Discovered By: Smithson Tennant
Appearance: silvery white
Category: transition metal
Melting Point: 2719 K
Boiling Point: 4403 K
Ox. State: -3, -1, 1, 2, 3, 4, 5, 6
Bonding Type: metallic
Electronegativity: 2.2
Wiki Link: Source Link
Element Image: Image Link

Iridium is a chemical element with symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, iridium is generally credited with being the second densest element (after osmium) based on measured density, although calculations involving the space lattices of the elements show that iridium is denser. It is also the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable.

Platinum

Discovered	State
Ancient	Solid
Atomic Mass	Density
195.0849	21.45 g/L

¹⁹⁵ ₇₈ Pt

Electrons	Protons	Neutrons
78	78	117
Electronic Configuration
[Xe] 4f¹⁴5d⁹6s¹

Discovered By: Antonio de Ulloa
Appearance: silvery white
Category: transition metal
Melting Point: 2041.4 K
Boiling Point: 4098 K
Ox. State: 2, 4, 5, 6
Bonding Type: metallic
Electronegativity: 2.28
Wiki Link: Source Link
Element Image: Image Link

Platinum is a chemical element with symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, gray-white transition metal. Its name is derived from the Spanish term platina, which is literally translated into "little silver".

Gold

Discovered	State
Ancient	Solid
Atomic Mass	Density
196.9665695	19.3 g/L

¹⁹⁷ ₇₉ Au

Electrons	Protons	Neutrons
79	79	118
Electronic Configuration
[Xe] 4f¹⁴5d¹⁰6s¹

Discovered By: Middle East
Appearance: metallic yellow
Category: transition metal
Melting Point: 1337.33 K
Boiling Point: 3243 K
Ox. State: -1, 1, 2, 3, 5
Bonding Type: metallic
Electronegativity: 2.54
Wiki Link: Source Link
Element Image: Image Link

Gold is a chemical element with symbol Au (from Latin:aurum) and atomic number 79. In its purest form, it is a bright, slightly reddish yellow, dense, soft, malleable and ductile metal. Chemically, gold is a transition metal and a group 11 element.

Mercury

Discovered	State
Ancient	Liquid
Atomic Mass	Density
200.5923	13.534 g/L

²⁰¹ ₈₀ Hg

Electrons	Protons	Neutrons
80	80	121
Electronic Configuration
[Xe] 4f¹⁴5d¹⁰6s²

Discovered By: unknown, before 2000 BCE
Appearance: silvery
Category: transition metal
Melting Point: 234.321 K
Boiling Point: 629.88 K
Ox. State: 1, 2, 4
Bonding Type: metallic
Electronegativity: 2
Wiki Link: Source Link
Element Image: Image Link

Mercury is a chemical element with symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum (/haɪˈdrɑːrdʒərəm/). A heavy, silvery d-block element, mercury is the only metallic element that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature.

Thallium

Discovered	State
1861	Solid
Atomic Mass	Density
204.38	11.85 g/L

²⁰⁴ ₈₁ Tl

Electrons	Protons	Neutrons
81	81	123
Electronic Configuration
[Xe] 4f¹⁴5d¹⁰6s²6p¹

Discovered By: William Crookes
Appearance: silvery white
Category: post-transition metal
Melting Point: 577 K
Boiling Point: 1746 K
Ox. State: 1, 3
Bonding Type: metallic
Electronegativity: 2.04
Wiki Link: Source Link
Element Image: Image Link

Thallium is a chemical element with symbol Tl and atomic number 81. This soft gray post-transition metal is not found free in nature. When isolated, it resembles tin, but discolors when exposed to air.

Lead

Discovered	State
Ancient	Solid
Atomic Mass	Density
207.21	11.34 g/L

²⁰⁸ ₈₂ Pb

Electrons	Protons	Neutrons
82	82	126
Electronic Configuration
[Xe] 4f¹⁴5d¹⁰6s²6p²

Discovered By: Middle East
Appearance: metallic gray
Category: post-transition metal
Melting Point: 600.61 K
Boiling Point: 2022 K
Ox. State: -4, 2, 4
Bonding Type: metallic
Electronegativity: 2.33
Wiki Link: Source Link
Element Image: Image Link

Lead (/lɛd/) is a chemical element in the carbon group with symbol Pb (from Latin:plumbum) and atomic number 82. Lead is a soft, malleable and heavy post-transition metal. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air.

Bismuth

Discovered	State
Ancient	Solid
Atomic Mass	Density
208.980401	9.78 g/L

²⁰⁶ ₈₃ Bi

Electrons	Protons	Neutrons
83	83	123
Electronic Configuration
[Xe] 4f¹⁴5d¹⁰6s²6p³

Discovered By: Claude François Geoffroy
Appearance: lustrous silver
Category: post-transition metal
Melting Point: 544.7 K
Boiling Point: 1837 K
Ox. State: -3, 3, 5
Bonding Type: metallic
Electronegativity: 2.02
Wiki Link: Source Link
Element Image: Image Link

Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a pentavalent post-transition metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally, although its sulfide and oxide form important commercial ores.

Polonium

Discovered	State
1898	Solid
Atomic Mass	Density
209	9.196 g/L

²⁰⁹ ₈₄ Po

Electrons	Protons	Neutrons
84	84	125
Electronic Configuration
[Xe] 4f¹⁴5d¹⁰6s²6p⁴

Discovered By: Pierre Curie
Appearance: silvery
Category: post-transition metal
Melting Point: 527 K
Boiling Point: 1235 K
Ox. State: -2, 2, 4, 6
Bonding Type: metallic
Electronegativity: 2
Wiki Link: Source Link
Element Image: Image Link

Polonium is a chemical element with symbol Po and atomic number 84, discovered in 1898 by Marie Curie and Pierre Curie. A rare and highly radioactive element with no stable isotopes, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Applications of polonium are few.

Astatine

Discovered	State
1940	Solid
Atomic Mass	Density
210	26.35 g/L

²¹⁰ ₈₅ At

Electrons	Protons	Neutrons
85	85	125
Electronic Configuration
[Xe] 4f¹⁴5d¹⁰6s²6p⁵

Discovered By: Dale R. Corson
Appearance: silvery
Category: metalloid
Melting Point: 575 K
Boiling Point: 610 K
Ox. State: -1, 1, 3, 5
Bonding Type: metallic
Electronegativity: 2.2
Wiki Link: Source Link
Element Image: Image Link

Astatine is a very rare radioactive chemical element with the chemical symbol At and atomic number 85. It occurs on Earth as the decay product of various heavier elements. All its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours.

Radon

Discovered	State
1900	Gas
Atomic Mass	Density
222	9.73 g/L

²²² ₈₆ Rn

Electrons	Protons	Neutrons
86	86	136
Electronic Configuration
[Xe] 4f¹⁴5d¹⁰6s²6p⁶

Discovered By: Friedrich Ernst Dorn
Appearance: colorless gas
Category: noble gas
Melting Point: 202 K
Boiling Point: 211.5 K
Ox. State: 2
Bonding Type: metallic
Electronegativity:
Wiki Link: Source Link
Element Image: Image Link

Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as a decay product of radium. Its most stable isotope, 222Rn, has a half-life of 3.8 days.

Francium

Discovered	State
1939	Solid
Atomic Mass	Density
223	1.87 g/L

²²³ ₈₇ Fr

Electrons	Protons	Neutrons
87	87	136
Electronic Configuration
[Rn] 7s¹

Discovered By: Marguerite Perey
Appearance:
Category: alkali metal
Melting Point: 300 K
Boiling Point: 950 K
Ox. State: 1
Bonding Type: metallic
Electronegativity: 0.7
Wiki Link: Source Link
Element Image: Image Link

Francium is a chemical element with symbol Fr and atomic number 87. It used to be known as eka-caesium and actinium K. It is the second-least electronegative element, behind only caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon.

Radium

Discovered	State
1898	Solid
Atomic Mass	Density
226	5.5 g/L

²²⁶ ₈₈ Ra

Electrons	Protons	Neutrons
88	88	138
Electronic Configuration
[Rn] 7s²

Discovered By: Pierre Curie
Appearance:
Category: alkaline earth metal
Melting Point: 1233 K
Boiling Point: 2010 K
Ox. State: 3
Bonding Type: metallic
Electronegativity: 0.9
Wiki Link: Source Link
Element Image: Image Link

Radium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is almost colorless, but it readily combines with nitrogen (rather than oxygen) on exposure to air, forming a black surface layer of radium nitride (Ra3N2).

Actinium

Discovered	State
1898	Solid
Atomic Mass	Density
226	10 g/L

²²⁷ ₈₉ Ac

Electrons	Protons	Neutrons
89	89	138
Electronic Configuration
[Rn] 6d¹7s²

Discovered By: Friedrich Oskar Giesel
Appearance:
Category: actinide
Melting Point: 1500 K
Boiling Point: 3500 K
Ox. State: 3
Bonding Type: metallic
Electronegativity: 1.1
Wiki Link: Source Link
Element Image: Image Link

Actinium is a radioactive chemical element with symbol Ac (not to be confused with the abbreviation for an acetyl group) and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902.

Thorium

Discovered	State
1828	Solid
Atomic Mass	Density
232.03774	11.724 g/L

²³² ₉₀ Th

Electrons	Protons	Neutrons
90	90	142
Electronic Configuration
[Rn] 6d²7s²

Discovered By: Jöns Jakob Berzelius
Appearance: silvery
Category: actinide
Melting Point: 2023 K
Boiling Point: 5061 K
Ox. State: 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Thorium is a chemical element with symbol Th and atomic number 90. A radioactive actinide metal, thorium is one of only two significantly radioactive elements that still occur naturally in large quantities as a primordial element (the other being uranium). It was discovered in 1828 by the Norwegian Reverend and amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jakob Berzelius, who named it after Thor, the Norse god of thunder.

Protactinium

Discovered	State
1913	Solid
Atomic Mass	Density
231.035882	15.37 g/L

²³¹ ₉₁ Pa

Electrons	Protons	Neutrons
91	91	140
Electronic Configuration
[Rn] 5f² 6d¹ 7s²

Discovered By: William Crookes
Appearance: bright, silvery metallic luster
Category: actinide
Melting Point: 1841 K
Boiling Point: 4300 K
Ox. State: 3, 4, 5
Bonding Type: metallic
Electronegativity: 1.5
Wiki Link: Source Link
Element Image: Image Link

Protactinium is a chemical element with symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume +4 and even +2 or +3 states.

Uranium

Discovered	State
1789	Solid
Atomic Mass	Density
238.028913	19.1 g/L

²³⁸ ₉₂ U

Electrons	Protons	Neutrons
92	92	146
Electronic Configuration
[Rn] 5f³ 6d¹ 7s²

Discovered By: Martin Heinrich Klaproth
Appearance:
Category: actinide
Melting Point: 1405.3 K
Boiling Point: 4404 K
Ox. State: 3, 4, 5, 6
Bonding Type: metallic
Electronegativity: 1.38
Wiki Link: Source Link
Element Image: Image Link

Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-white metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons.

Neptunium

Discovered	State
1940	Solid
Atomic Mass	Density
237	20.45 g/L

²³⁷ ₉₃ Np

Electrons	Protons	Neutrons
93	93	144
Electronic Configuration
[Rn] 5f³ 6d¹ 7s²

Discovered By: Edwin McMillan
Appearance:
Category: actinide
Melting Point: 912 K
Boiling Point: 4447 K
Ox. State: 3, 4, 5, 6, 7
Bonding Type: metallic
Electronegativity: 1.36
Wiki Link: Source Link
Element Image: Image Link

Neptunium is a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus.

Plutonium

Discovered	State
1940	Solid
Atomic Mass	Density
244	19.816 g/L

³³³ ₉₄ Pu

Electrons	Protons	Neutrons
94	94	239
Electronic Configuration
[Rn] 5f⁶ 7s²

Discovered By: Glenn T. Seaborg
Appearance: silvery white
Category: actinide
Melting Point: 912.5 K
Boiling Point: 3505 K
Ox. State: 3, 4, 5, 6, 7
Bonding Type: metallic
Electronegativity: 1.28
Wiki Link: Source Link
Element Image: Image Link

Plutonium is a transuranic radioactive chemical element with symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states.

Americium

Discovered	State
1944	Solid
Atomic Mass	Density
243	12 g/L

²⁴³ ₉₅ Am

Electrons	Protons	Neutrons
95	95	148
Electronic Configuration
[Rn] 5f⁷ 7s²

Discovered By: Glenn T. Seaborg
Appearance: silvery white
Category: actinide
Melting Point: 1449 K
Boiling Point: 2880 K
Ox. State: 3, 4, 5, 6, 7
Bonding Type: metallic
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Americium is a radioactive transuranic chemical element with symbol Am and atomic number 95. This member of the actinide series is located in the periodic table under the lanthanide element europium, and thus by analogy was named after the Americas. Americium was first produced in 1944 by the group of Glenn T.Seaborg from Berkeley, California, at the metallurgical laboratory of University of Chicago.

Curium

Discovered	State
1944	Solid
Atomic Mass	Density
247	13.51 g/L

²⁴⁷ ₉₆ Cm

Electrons	Protons	Neutrons
96	96	151
Electronic Configuration
[Rn] 5f⁷ 6d¹ 7s²

Discovered By: Glenn T. Seaborg
Appearance: silvery metallic
Category: actinide
Melting Point: 1613 K
Boiling Point: 3383 K
Ox. State: 3, 4
Bonding Type: metallic
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Curium is a transuranic radioactive chemical element with symbol Cm and atomic number 96. This element of the actinide series was named after Marie and Pierre Curie – both were known for their research on radioactivity. Curium was first intentionally produced and identified in July 1944 by the group of Glenn T. Seaborg at the University of California, Berkeley.

Berkelium

Discovered	State
1949	Solid
Atomic Mass	Density
247	14.78 g/L

²⁴⁷ ₉₇ Bk

Electrons	Protons	Neutrons
97	97	150
Electronic Configuration
[Rn] 5f⁹ 7s²

Discovered By: Lawrence Berkeley National Laboratory
Appearance: silvery
Category: actinide
Melting Point: 1259 K
Boiling Point: 2900 K
Ox. State: 3, 4
Bonding Type: metallic
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Berkelium is a transuranic radioactive chemical element with symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the University of California Radiation Laboratory where it was discovered in December 1949.

Californium

Discovered	State
1950	Solid
Atomic Mass	Density
251	15.1 g/L

²⁵¹ ₉₈ Cf

Electrons	Protons	Neutrons
98	98	153
Electronic Configuration
[Rn] 5f¹⁰ 7s²

Discovered By: Lawrence Berkeley National Laboratory
Appearance: silvery
Category: actinide
Melting Point: 1173 K
Boiling Point: 1743 K
Ox. State: 2, 3, 4
Bonding Type: metallic
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Californium is a radioactive metallic chemical element with symbol Cf and atomic number 98. The element was first made in 1950 at the University of California Radiation Laboratory in Berkeley, by bombarding curium with alpha particles (helium-4 ions). It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium).

Einsteinium

Discovered	State
1950	Solid
Atomic Mass	Density
252	8.84 g/L

²⁵² ₉₉ Es

Electrons	Protons	Neutrons
99	99	153
Electronic Configuration
[Rn] 5f¹¹ 7s²

Discovered By: Lawrence Berkeley National Laboratory
Appearance: silvery
Category: actinide
Melting Point: 1133 K
Boiling Point: 1269 K
Ox. State: 2, 3
Bonding Type: metallic
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Einsteinium is a synthetic element with symbol Es and atomic number 99. It is the seventh transuranic element, and an actinide. Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein.

Fermium

Discovered	State
1952	Solid
Atomic Mass	Density
257	g/L

²⁵⁷ ₁₀₀ Fm

Electrons	Protons	Neutrons
100	100	157
Electronic Configuration
[Rn] 5f¹² 7s²

Discovered By: Lawrence Berkeley National Laboratory
Appearance:
Category: actinide
Melting Point: 1800 K
Boiling Point: K
Ox. State: 2, 3
Bonding Type:
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Fermium is a synthetic element with symbol Fm and atomic number 100. It is a member of the actinide series. It is the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities, although pure fermium metal has not yet been prepared.

Mendelevium

Discovered	State
1955	Solid
Atomic Mass	Density
258	g/L

²⁵⁸ ₁₀₁ Md

Electrons	Protons	Neutrons
101	101	157
Electronic Configuration
[Rn] 5f¹³ 7s²

Discovered By: Lawrence Berkeley National Laboratory
Appearance:
Category: actinide
Melting Point: 1100 K
Boiling Point: K
Ox. State: 2, 3
Bonding Type:
Electronegativity: 1.3
Wiki Link: Source Link
Element Image: Image Link

Mendelevium is a synthetic element with chemical symbol Md (formerly Mv) and atomic number 101. A metallic radioactive transuranic element in the actinide series, it is the first element that currently cannot be produced in macroscopic quantities through neutron bombardment of lighter elements. It is the antepenultimate actinide and the ninth transuranic element.

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