Argon

• Argon, symbol Ar, inert gaseous element that is the third most prevalent gas in Earth's atmosphere. In group 18 (or VIIIa) of the periodic table , argon is one of the noble gases. The atomic number of argon is 18. The element’s name comes from the Greek word argos, "inactive," because argon does not easily react with other elements.

• Argon was discovered in 1894 by the British scientists Sir William Ramsay and Baron John William Strutt Rayleigh. They were led to this discovery by a discrepancy between the density of supposedly pure nitrogen, prepared from air, and actually pure nitrogen, prepared from ammonium nitrate. Argon is composed of monatomic molecules and is colorless and odorless. It constitutes 0.93 percent of the atmosphere. Argon melts at -189.3°C (-308.2°F) and boils at -185.86°C (-302.55°F). The atomic weight of argon is 39.948.

• In recent years chemists have been able to force most of the noble gases to form compounds. Researchers at the University of Helsinki achieved this feat with argon in 2000. They created argon fluorohydride (HArF) by shining ultraviolet light on frozen argon containing a small amount of hydrogen fluoride.

• Argon is produced commercially by the fractional distillation of liquid air. It is used in large quantities to fill electric light bulbs. If air is left in incandescent bulbs, the filament burns; if the bulb is evacuated, as was formerly done, the tungsten filament tends to evaporate, blackening the inside of the bulb. To prevent this evaporation, the bulb can be filled with nitrogen, which is the least expensive gas for the purpose, or argon, which is better, as it is a poorer conductor of heat and so cools the filament less.

• Argon is also used in one type of neon lamp. Whereas pure neon gives a red light, argon gives a blue light. Argon tubes require a lower voltage than neon tubes, and for this reason small amounts of argon are sometimes mixed with neon. Argon is also used in electric-arc technology, in gas lasers, and in arc welding.

Elements of the Periodic Table

Elements Sorted by Name

Name

Symbol

Atomic Number

Atomic Weight

Group

Date Discovered

Discovered By

Actinium	Ac	89	(227)	Actinide series	1899	André Debierne
Aluminum	Al	13	26.9815	Other metals	1824	Hans Oersted (also attributed to Friedrich Wöhler 1827)
Americium	Am	95	243	Actinide series	1944	Glenn Seaborg, Ralph James, Leon Morgan, and Albert Ghiorso
Antimony	Sb	51	121.760	Other metals	prehistoric	unknown
Argon	Ar	18	39.948	Noble gases	1894	John Rayleigh and William Ramsay
Arsenic	As	33	74.9216	Nonmetals	prehistoric	unknown
Astatine	At	85	(210)	Halogens	1940	Dale R. Corson, K. R. MacKenzie, and Emilio Segrè
Barium	Ba	56	137.328	Alkaline earth metals	1808	Humphry Davy
Berkelium	Bk	97	(247)	Actinide series	1949	Glenn Seaborg, Stanley Thompson, and Albert Ghiorso
Beryllium	Be	4	9.0122	Alkaline earth metals	1798	Louis-Nicolas Vauquelin (isolated by Friedrich Wöhler and Antoine-Alexandre-Brutus Bussy 1828)
Bismuth	Bi	83	208.9804	Other metals	prehistoric	unknown
Bohrium	Bh	107	(262)	Transition metals	1976	Georgii Flerov and Yuri Oganessian (confirmed by German scientist Peter Armbruster and coworkers)
Boron	B	5	10.81	Nonmetals	1808	Humphry Davy, and independently by Joseph Gay-Lussac and Louis-Jacques Thénard
Bromine	Br	35	79.904	Halogens	1826	Antoine-Jérôme Balard
Cadmium	Cd	48	112.412	Transition metals	1817	Friedrich Strohmeyer
Calcium	Ca	20	40.078	Alkaline earth metals	1808	Humphry Davy
Californium	Cf	98	(251)	Actinide series	1950	Glenn Seaborg, Stanley Thompson, Kenneth Street, Jr., and Albert Ghiorso
Carbon	C	6	12.011	Nonmetals	prehistoric	unknown
Cerium	Ce	58	140.115	Lanthanide series	1804	Jöns Berzelius and Wilhelm Hisinger, and independently by Martin Klaproth
Cesium	Cs	55	132.9054	Alkali metals	1860	Robert Bunsen and Gustav Kirchhoff
Chlorine	Cl	17	35.4528	Halogens	1774	Karl Scheele
Chromium	Cr	24	51.9962	Transition metals	1797	Louis-Nicolas Vauquelin
Cobalt	Co	27	58.9332	Transition metals	1730	Georg Brandt
Copper	Cu	29	63.546	Transition metals	prehistoric	unknown
Curium	Cm	96	(247)	Actinide series	1944	Glenn Seaborg, Ralph James, and Albert Ghiorso
Darmstadtium	Ds	110	(271)	Transition metals	1994	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
Dubnium	Db	105	(262)	Transition metals	1970	claimed by Albert Ghiorso and coworkers (disputed by Soviet workers)
Dysprosium	Dy	66	162.500	Lanthanide series	1886	Paul Lecoq de Boisbaudran
Einsteinium	Es	99	(252)	Actinide series	1952	Albert Ghiorso and coworkers
Erbium	Er	68	167.26	Lanthanide series	1843	Carl Mosander
Europium	Eu	63	151.966	Lanthanide series	1901	Eugène Demarçay
Fermium	Fm	100	(257)	Actinide series	1955	Albert Ghiorso and coworkers
Fluorine	F	9	18.9984	Halogens	1771	Karl Scheele (isolated by Henri Moissan 1886)
Francium	Fr	87	(223)	Alkali metals	1939	Marguérite Perey
Gadolinium	Gd	64	157.25	Lanthanide series	1886	Paul Lecoq de Boisbaudran
Gallium	Ga	31	69.723	Other metals	1875	Paul Lecoq de Boisbaudran
Germanium	Ge	32	72.61	Other metals	1886	Clemens Winkler
Gold	Au	79	196.9665	Transition metals	prehistoric	unknown
Hafnium	Hf	72	178.49	Transition metals	1913	Dirk Coster and Georg von Hevesy
Hassium	Hs	108	(263)	Transition metals	1984	Peter Armbruster and coworkers
Helium	He	2	4.0026	Noble gases	1868	Pierre Janssen
Holmium	Ho	67	164.9303	Lanthanide series	1879	Per Cleve
Hydrogen	H	1	1.0079	Nonmetals	1766	Henry Cavendish
Indium	In	49	114.818	Other metals	1863	Ferdinand Reich and Hieronymus Richter
Iodine	I	53	126.9045	Halogens	1811	Bernard Courtois
Iridium	Ir	77	192.217	Transition metals	1804	Smithson Tennant
Iron	Fe	26	55.845	Transition metals	prehistoric	unknown
Krypton	Kr	36	83.798	Noble gases	1898	William Ramsay and Morris Travers
Lanthanum	La	57	138.9055	Lanthanide series	1839	Carl Mosander
Lawrencium	Lr	103	(260)	Transition metals	1961	Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh, and Robert Latimer
Lead	Pb	82	207.2	Other metals	prehistoric	unknown
Lithium	Li	3	6.941	Alkali metals	1817	Johan Arfwedson
Lutetium	Lu	71	174.967	Transition metals	1907	Georges Urbain and Carl von Welsbach, independently of each other
Magnesium	Mg	12	24.3051	Alkaline earth metals	1755	Joseph Black (oxide isolated by Humphry Davy 1808; pure form isolated by Antoine-Alexandre-Brutus Bussy 1828)
Manganese	Mn	25	54.938	Transition metals	1774	Johann Gottlieb Gahn
Meitnerium	Mt	109	(268)	Transition metals	1982	Peter Armbruster and coworkers
Mendelevium	Md	101	(258)	Actinide series	1955	Albert Ghiorso, Bernard G. Harvey, Gregory Choppin, Stanley Thompson, and Glenn Seaborg
Mercury	Hg	80	200.59	Transition metals	prehistoric	unknown
Molybdenum	Mo	42	95.94	Transition metals	1781	named by Karl Scheele (isolated by Peter Jacob Hjelm 1782)
Neodymium	Nd	60	144.24	Lanthanide series	1885	Carl von Welsbach
Neon	Ne	10	20.1798	Noble gases	1898	William Ramsay and Morris Travers
Neptunium	Np	93	(237)	Actinide series	1940	Edwin McMillan and Philip Abelson
Nickel	Ni	28	58.6934	Transition metals	1751	Axel Cronstedt
Niobium	Nb	41	92.9064	Transition metals	1801	Charles Hatchett
Nitrogen	N	7	14.0067	Nonmetals	1772	Daniel Rutherford
Nobelium	No	102	(259)	Actinide series	1958	Albert Ghiorso, Torbjørn Sikkeland, J. R. Walton, and Glenn Seaborg
Osmium	Os	76	190.23	Transition metals	1804	Smithson Tennant
Oxygen	O	8	15.9994	Nonmetals	1774	Joseph Priestley and Karl Scheele, independently of each other
Palladium	Pd	46	106.42	Transition metals	1804	William Wollaston
Phosphorus	P	15	30.9738	Nonmetals	1674	Hennig Brand
Platinum	Pt	78	195.08	Transition metals	1557	Julius Scaliger
Plutonium	Pu	94	(244)	Actinide series	1940	Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl
Polonium	Po	84	(209)	Other metals	1898	Marie and Pierre Curie
Potassium	K	19	39.0983	Alkali metals	1807	Humphry Davy
Praseodymium	Pr	59	140.908	Lanthanide series	1885	Carl von Welsbach
Promethium	Pm	61	(145)	Lanthanide series	1945	J. A. Marinsky, Lawrence Glendenin, and Charles Coryell
Protactinium	Pa	91	231.036	Actinide series	1913	Kasimir Fajans and O. Göhring
Radium	Ra	88	(226)	Alkaline earth metals	1898	Marie Curie
Radon	Rn	86	(222)	Noble gases	1900	Friedrich Dorn
Rhenium	Re	75	186.207	Transition metals	1925	Walter Noddack, Ida Tacke, and Otto Berg
Rhodium	Rh	45	102.9055	Transition metals	1804	William Wollaston
Rubidium	Rb	37	85.4678	Alkali metals	1861	Robert Bunsen and Gustav Kirchhoff
Ruthenium	Ru	44	101.07	Transition metals	1827	G. W. Osann (isolated by Karl Klaus 1844)
Rutherfordium	Rf	104	(261)	Transition metals	1969	claimed by U.S. scientist Albert Ghiorso and coworkers (disputed by Soviet workers)
Samarium	Sm	62	150.36	Lanthanide series	1879	Paul Lecoq de Boisbaudran
Scandium	Sc	21	44.9559	Transition metals	1876	Lars Nilson
Seaborgium	Sg	106	(266)	Transition metals	1974	claimed by Georgii Flerov and coworkers, and independently by Albert Ghiorso and coworkers
Selenium	Se	34	78.96	Nonmetals	1817	Jöns Berzelius
Silicon	Si	14	28.0855	Nonmetals	1823	Johan Arfwedson
Silver	Ag	47	107.8682	Transition metals	prehistoric	unknown
Sodium	Na	11	22.9898	Alkali metals	1807	Humphry Davy
Strontium	Sr	38	87.62	Alkaline earth metals	1808	Humphry Davy
Sulfur	S	16	32.067	Nonmetals	prehistoric	unknown
Tantalum	Ta	73	180.948	Transition metals	1802	Anders Ekeberg
Technetium	Tc	43	(98)	Transition metals	1937	Carlo Perrier and Emilio Segrè
Tellurium	Te	52	127.60	Nonmetals	1782	Franz Müller
Terbium	Tb	65	158.9253	Lanthanide series	1843	Carl Mosander
Thallium	Tl	81	204.3833	Other metals	1861	William Crookes (isolated by William Crookes and Claude August Lamy, independently of each other, in 1862)
Thorium	Th	90	232.0381	Actinide series	1828	Jöns Berzelius
Thulium	Tm	69	168.9342	Lanthanide series	1879	Per Cleve
Tin	Sn	50	118.711	Other metals	prehistoric	unknown
Titanium	Ti	22	47.867	Transition metals	1790	William Gregor
Tungsten	W	74	183.84	Transition metals	1783	isolated by Juan José Elhuyar and Fausto Elhuyar
Ununbium	Uub	112	(277)	Transition metals	1996	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
Ununhexium	Uuh	116	(292)	Other metals	2000	team at the Joint Institute for Nuclear Research, Dubna, Russia
Ununquadium	Uuq	114	(285)	Other metals	1998	team at the Joint Institute for Nuclear Research, Dubna, Russia
Roentgenium	Rg	111	(272)	Transition metals	1994	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
Uranium	U	92	238.0289	Actinide series	1789	Martin Klaproth (isolated by Eugène Péligot 1841)
Vanadium	V	23	50.9415	Transition metals	1801	Andrés del Rio (disputed), or Nils Sefström 1830
Xenon	Xe	54	131.29	Noble gases	1898	William Ramsay and Morris Travers
Ytterbium	Yb	70	173.04	Lanthanide series	1878	Jean Charles de Marignac
Yttrium	Y	39	88.906	Transition metals	1794	Johan Gadolin
Zinc	Zn	30	65.409	Transition metals	prehistoric	unknown
Zirconium	Zr	40	91.224	Transition metals	1789	Martin Klaproth

Elements Sorted by Atomic Number

Atomic Number

Name

Symbol

Atomic Weight

Group

Date Discovered

Discovered By

1	Hydrogen	H	1.0079	Nonmetals	1766	Henry Cavendish
2	Helium	He	4.0026	Noble gases	1868	Pierre Janssen
3	Lithium	Li	6.941	Alkali metals	1817	Johan Arfwedson
4	Beryllium	Be	9.0122	Alkaline earth metals	1798	Louis-Nicolas Vauquelin (isolated by Friedrich Wöhler and Antoine-Alexandre-Brutus Bussy 1828)
5	Boron	B	10.81	Nonmetals	1808	Humphry Davy, and independently by Joseph Gay-Lussac and Louis-Jacques Thénard
6	Carbon	C	12.011	Nonmetals	prehistoric	unknown
7	Nitrogen	N	14.0067	Nonmetals	1772	Daniel Rutherford
8	Oxygen	O	15.9994	Nonmetals	1774	Joseph Priestley and Karl Scheele, independently of each other
9	Fluorine	F	18.9984	Halogens	1771	Karl Scheele (isolated by Henri Moissan 1886)
10	Neon	Ne	20.1798	Noble gases	1898	William Ramsay and Morris Travers
11	Sodium	Na	22.9898	Alkali metals	1807	Humphry Davy
12	Magnesium	Mg	24.3051	Alkaline earth metals	1755	Joseph Black (oxide isolated by Humphry Davy 1808; pure form isolated by Antoine-Alexandre-Brutus Bussy 1828)
13	Aluminum	Al	26.9815	Other metals	1824	Hans Oersted (also attributed to Friedrich Wöhler 1827)
14	Silicon	Si	28.0855	Nonmetals	1823	Johan Arfwedson
15	Phosphorus	P	30.9738	Nonmetals	1674	Hennig Brand
16	Sulfur	S	32.067	Nonmetals	prehistoric	unknown
17	Chlorine	Cl	35.4528	Halogens	1774	Karl Scheele
18	Argon	Ar	39.948	Noble gases	1894	John Rayleigh and William Ramsay
19	Potassium	K	39.0983	Alkali metals	1807	Humphry Davy
20	Calcium	Ca	40.078	Alkaline earth metals	1808	Humphry Davy
21	Scandium	Sc	44.9559	Transition metals	1876	Lars Nilson
22	Titanium	Ti	47.867	Transition metals	1790	William Gregor
23	Vanadium	V	50.9415	Transition metals	1801	Andrés del Rio (disputed), or Nils Sefström 1830
24	Chromium	Cr	51.9962	Transition metals	1797	Louis-Nicolas Vauquelin
25	Manganese	Mn	54.938	Transition metals	1774	Johann Gottlieb Gahn
26	Iron	Fe	55.845	Transition metals	prehistoric	unknown
27	Cobalt	Co	58.9332	Transition metals	1730	Georg Brandt
28	Nickel	Ni	58.6934	Transition metals	1751	Axel Cronstedt
29	Copper	Cu	63.546	Transition metals	prehistoric	unknown
30	Zinc	Zn	65.409	Transition metals	prehistoric	unknown
31	Gallium	Ga	69.723	Other metals	1875	Paul Lecoq de Boisbaudran
32	Germanium	Ge	72.61	Other metals	1886	Clemens Winkler
33	Arsenic	As	74.9216	Nonmetals	prehistoric	unknown
34	Selenium	Se	78.96	Nonmetals	1817	Jöns Berzelius
35	Bromine	Br	79.904	Halogens	1826	Antoine-Jérôme Balard
36	Krypton	Kr	83.798	Noble gases	1898	William Ramsay and Morris Travers
37	Rubidium	Rb	85.4678	Alkali metals	1861	Robert Bunsen and Gustav Kirchhoff
38	Strontium	Sr	87.62	Alkaline earth metals	1808	Humphry Davy
39	Yttrium	Y	88.906	Transition metals	1794	Johan Gadolin
40	Zirconium	Zr	91.224	Transition metals	1789	Martin Klaproth
41	Niobium	Nb	92.9064	Transition metals	1801	Charles Hatchett
42	Molybdenum	Mo	95.94	Transition metals	1781	named by Karl Scheele (isolated by Peter Jacob Hjelm 1782)
43	Technetium	Tc	(98)	Transition metals	1937	Carlo Perrier and Emilio Segrè
44	Ruthenium	Ru	101.07	Transition metals	1827	G. W. Osann (isolated by Karl Klaus 1844)
45	Rhodium	Rh	102.9055	Transition metals	1804	William Wollaston
46	Palladium	Pd	106.42	Transition metals	1804	William Wollaston
47	Silver	Ag	107.8682	Transition metals	prehistoric	unknown
48	Cadmium	Cd	112.412	Transition metals	1817	Friedrich Strohmeyer
49	Indium	In	114.818	Other metals	1863	Ferdinand Reich and Hieronymus Richter
50	Tin	Sn	118.711	Other metals	prehistoric	unknown
51	Antimony	Sb	121.760	Other metals	prehistoric	unknown
52	Tellurium	Te	127.60	Nonmetals	1782	Franz Müller
53	Iodine	I	126.9045	Halogens	1811	Bernard Courtois
54	Xenon	Xe	131.29	Noble gases	1898	William Ramsay and Morris Travers
55	Cesium	Cs	132.9054	Alkali metals	1860	Robert Bunsen and Gustav Kirchhoff
56	Barium	Ba	137.328	Alkaline earth metals	1808	Humphry Davy
57	Lanthanum	La	138.9055	Lanthanide series	1839	Carl Mosander
58	Cerium	Ce	140.115	Lanthanide series	1804	Jöns Berzelius and Wilhelm Hisinger, and independently by Martin Klaproth
59	Praseodymium	Pr	140.908	Lanthanide series	1885	Carl von Welsbach
60	Neodymium	Nd	144.24	Lanthanide series	1885	Carl von Welsbach
61	Promethium	Pm	(145)	Lanthanide series	1945	J. A. Marinsky, Lawrence Glendenin, and Charles Coryell
62	Samarium	Sm	150.36	Lanthanide series	1879	Paul Lecoq de Boisbaudran
63	Europium	Eu	151.966	Lanthanide series	1901	Eugène Demarçay
64	Gadolinium	Gd	157.25	Lanthanide series	1886	Paul Lecoq de Boisbaudran
65	Terbium	Tb	158.9253	Lanthanide series	1843	Carl Mosander
66	Dysprosium	Dy	162.500	Lanthanide series	1886	Paul Lecoq de Boisbaudran
67	Holmium	Ho	164.9303	Lanthanide series	1879	Per Cleve
68	Erbium	Er	167.26	Lanthanide series	1843	Carl Mosander
69	Thulium	Tm	168.9342	Lanthanide series	1879	Per Cleve
70	Ytterbium	Yb	173.04	Lanthanide series	1878	Jean Charles de Marignac
71	Lutetium	Lu	174.967	Transition metals	1907	Georges Urbain and Carl von Welsbach, independently of each other
72	Hafnium	Hf	178.49	Transition metals	1913	Dirk Coster and Georg von Hevesy
73	Tantalum	Ta	180.948	Transition metals	1802	Anders Ekeberg
74	Tungsten	W	183.84	Transition metals	1783	isolated by Juan José Elhuyar and Fausto Elhuyar
75	Rhenium	Re	186.207	Transition metals	1925	Walter Noddack, Ida Tacke, and Otto Berg
76	Osmium	Os	190.23	Transition metals	1804	Smithson Tennant
77	Iridium	Ir	192.217	Transition metals	1804	Smithson Tennant
78	Platinum	Pt	195.08	Transition metals	1557	Julius Scaliger
79	Gold	Au	196.9665	Transition metals	prehistoric	unknown
80	Mercury	Hg	200.59	Transition metals	prehistoric	unknown
81	Thallium	Tl	204.3833	Other metals	1861	William Crookes (isolated by William Crookes and Claude August Lamy, independently of each other, in 1862)
82	Lead	Pb	207.2	Other metals	prehistoric	unknown
83	Bismuth	Bi	208.9804	Other metals	prehistoric	unknown
84	Polonium	Po	(209)	Other metals	1898	Marie and Pierre Curie
85	Astatine	At	(210)	Halogens	1940	Dale R. Corson, K. R. MacKenzie, and Emilio Segrè
86	Radon	Rn	(222)	Noble gases	1900	Friedrich Dorn
87	Francium	Fr	(223)	Alkali metals	1939	Marguérite Perey
88	Radium	Ra	(226)	Alkaline earth metals	1898	Marie Curie
89	Actinium	Ac	(227)	Actinide series	1899	André Debierne
90	Thorium	Th	232.0381	Actinide series	1828	Jöns Berzelius
91	Protactinium	Pa	231.036	Actinide series	1913	Kasimir Fajans and O. Göhring
92	Uranium	U	238.0289	Actinide series	1789	Martin Klaproth (isolated by Eugène Péligot 1841)
93	Neptunium	Np	(237)	Actinide series	1940	Edwin McMillan and Philip Abelson
94	Plutonium	Pu	(244)	Actinide series	1940	Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl
95	Americium	Am	243	Actinide series	1944	Glenn Seaborg, Ralph James, Leon Morgan, and Albert Ghiorso
96	Curium	Cm	(247)	Actinide series	1944	Glenn Seaborg, Ralph James, and Albert Ghiorso
97	Berkelium	Bk	(247)	Actinide series	1949	Glenn Seaborg, Stanley Thompson, and Albert Ghiorso
98	Californium	Cf	(251)	Actinide series	1950	Glenn Seaborg, Stanley Thompson, Kenneth Street, Jr., and Albert Ghiorso
99	Einsteinium	Es	(252)	Actinide series	1952	Albert Ghiorso and coworkers
100	Fermium	Fm	(257)	Actinide series	1955	Albert Ghiorso and coworkers
101	Mendelevium	Md	(258)	Actinide series	1955	Albert Ghiorso, Bernard G. Harvey, Gregory Choppin, Stanley Thompson, and Glenn Seaborg
102	Nobelium	No	(259)	Actinide series	1958	Albert Ghiorso, Torbjørn Sikkeland, J. R. Walton, and Glenn Seaborg
103	Lawrencium	Lr	(260)	Transition metals	1961	Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh, and Robert Latimer
104	Rutherfordium	Rf	(261)	Transition metals	1969	claimed by U.S. scientist Albert Ghiorso and coworkers (disputed by Soviet workers)
105	Dubnium	Db	(262)	Transition metals	1970	claimed by Albert Ghiorso and coworkers (disputed by Soviet workers)
106	Seaborgium	Sg	(266)	Transition metals	1974	claimed by Georgii Flerov and coworkers, and independently by Albert Ghiorso and coworkers
107	Bohrium	Bh	(262)	Transition metals	1976	Georgii Flerov and Yuri Oganessian (confirmed by German scientist Peter Armbruster and coworkers)
108	Hassium	Hs	(263)	Transition metals	1984	Peter Armbruster and coworkers
109	Meitnerium	Mt	(268)	Transition metals	1982	Peter Armbruster and coworkers
110	Darmstadtium	Ds	(271)	Transition metals	1994	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
111	Roentgenium	Rg	(272)	Transition metals	1994	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
112	Ununbium	Uub	(277)	Transition metals	1996	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
114	Ununquadium	Uuq	(285)	Other metals	1998	team at the Joint Institute for Nuclear Research, Dubna, Russia
116	Ununhexium	Uuh	(292)	Other metals	2000	team at the Joint Institute for Nuclear Research, Dubna, Russia

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Antimony

• Antimony, symbol Sb, bluish-white, brittle, semimetalic element. The atomic number of antimony is 51; the element is in group 15 (or Va) of the periodic table (see Periodic Law).

• Antimony's compounds were known in ancient times, and the element was probably discovered by the German alchemist Basil Valentine about 1450. It was certainly known by about 1600, but was confused with other elements, such as bismuth, tin, and lead. The element’s name comes from the Greek words anti monos, meaning “not alone.” Antimony generally shows the properties of a metal, but sometimes shows those of a nonmetal. It exists in several distinctly different physical forms, the most common of which is metallic in appearance.

• Antimony ranks about 64th in natural abundance among the elements in crustal rock. The atomic weight of antimony is 121.76; it melts at about 631°C (about 1168°F), boils at about 1590°C (about 2890°F), and has a specific gravity of 6.7. It occasionally occurs as a free element, usually associated with silver, arsenic, or bismuth. It crystallizes in the hexagonal system (see Crystal), but crystals are rarely found. It has a hardness of 3. The principal ore of antimony is stibnite, a sulfide of antimony, which is mined in China, France, Italy, Japan, Mexico, and, on a small scale, in the western United States. Considerable amounts of antimony are produced as a by-product in the refining of ores of copper and lead.

• Liquid antimony has the exceptional property, when cooling, of expanding as it solidifies (water is one of the few other substances with this same property). It will thus fill in the crevices of a mold and yield castings of exceptionally sharp outlines. For this reason, it is used in making type metal; it is also a constituent of many other alloys, such as Britannia metal, pewter, Babbitt metal and antimonial lead.

• Among important compounds of antimony are tartar emetic, a double tartrate of antimony and potassium used as a medicinal agent; red antimony sulfide, used on safety matches and in vulcanizing rubber; glass of antimony, a mixture of antimony sulfide and oxide, used as a yellow pigment in glass and porcelain; and butter of antimony, antimony trichloride, used for bronzing steel, as a mordant in dyeing, and as a caustic in medicine.

Elements of the Periodic Table

Elements Sorted by Name

Name

Symbol

Atomic Number

Atomic Weight

Group

Date Discovered

Discovered By

Actinium	Ac	89	(227)	Actinide series	1899	André Debierne
Aluminum	Al	13	26.9815	Other metals	1824	Hans Oersted (also attributed to Friedrich Wöhler 1827)
Americium	Am	95	243	Actinide series	1944	Glenn Seaborg, Ralph James, Leon Morgan, and Albert Ghiorso
Antimony	Sb	51	121.760	Other metals	prehistoric	unknown
Argon	Ar	18	39.948	Noble gases	1894	John Rayleigh and William Ramsay
Arsenic	As	33	74.9216	Nonmetals	prehistoric	unknown
Astatine	At	85	(210)	Halogens	1940	Dale R. Corson, K. R. MacKenzie, and Emilio Segrè
Barium	Ba	56	137.328	Alkaline earth metals	1808	Humphry Davy
Berkelium	Bk	97	(247)	Actinide series	1949	Glenn Seaborg, Stanley Thompson, and Albert Ghiorso
Beryllium	Be	4	9.0122	Alkaline earth metals	1798	Louis-Nicolas Vauquelin (isolated by Friedrich Wöhler and Antoine-Alexandre-Brutus Bussy 1828)
Bismuth	Bi	83	208.9804	Other metals	prehistoric	unknown
Bohrium	Bh	107	(262)	Transition metals	1976	Georgii Flerov and Yuri Oganessian (confirmed by German scientist Peter Armbruster and coworkers)
Boron	B	5	10.81	Nonmetals	1808	Humphry Davy, and independently by Joseph Gay-Lussac and Louis-Jacques Thénard
Bromine	Br	35	79.904	Halogens	1826	Antoine-Jérôme Balard
Cadmium	Cd	48	112.412	Transition metals	1817	Friedrich Strohmeyer
Calcium	Ca	20	40.078	Alkaline earth metals	1808	Humphry Davy
Californium	Cf	98	(251)	Actinide series	1950	Glenn Seaborg, Stanley Thompson, Kenneth Street, Jr., and Albert Ghiorso
Carbon	C	6	12.011	Nonmetals	prehistoric	unknown
Cerium	Ce	58	140.115	Lanthanide series	1804	Jöns Berzelius and Wilhelm Hisinger, and independently by Martin Klaproth
Cesium	Cs	55	132.9054	Alkali metals	1860	Robert Bunsen and Gustav Kirchhoff
Chlorine	Cl	17	35.4528	Halogens	1774	Karl Scheele
Chromium	Cr	24	51.9962	Transition metals	1797	Louis-Nicolas Vauquelin
Cobalt	Co	27	58.9332	Transition metals	1730	Georg Brandt
Copper	Cu	29	63.546	Transition metals	prehistoric	unknown
Curium	Cm	96	(247)	Actinide series	1944	Glenn Seaborg, Ralph James, and Albert Ghiorso
Darmstadtium	Ds	110	(271)	Transition metals	1994	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
Dubnium	Db	105	(262)	Transition metals	1970	claimed by Albert Ghiorso and coworkers (disputed by Soviet workers)
Dysprosium	Dy	66	162.500	Lanthanide series	1886	Paul Lecoq de Boisbaudran
Einsteinium	Es	99	(252)	Actinide series	1952	Albert Ghiorso and coworkers
Erbium	Er	68	167.26	Lanthanide series	1843	Carl Mosander
Europium	Eu	63	151.966	Lanthanide series	1901	Eugène Demarçay
Fermium	Fm	100	(257)	Actinide series	1955	Albert Ghiorso and coworkers
Fluorine	F	9	18.9984	Halogens	1771	Karl Scheele (isolated by Henri Moissan 1886)
Francium	Fr	87	(223)	Alkali metals	1939	Marguérite Perey
Gadolinium	Gd	64	157.25	Lanthanide series	1886	Paul Lecoq de Boisbaudran
Gallium	Ga	31	69.723	Other metals	1875	Paul Lecoq de Boisbaudran
Germanium	Ge	32	72.61	Other metals	1886	Clemens Winkler
Gold	Au	79	196.9665	Transition metals	prehistoric	unknown
Hafnium	Hf	72	178.49	Transition metals	1913	Dirk Coster and Georg von Hevesy
Hassium	Hs	108	(263)	Transition metals	1984	Peter Armbruster and coworkers
Helium	He	2	4.0026	Noble gases	1868	Pierre Janssen
Holmium	Ho	67	164.9303	Lanthanide series	1879	Per Cleve
Hydrogen	H	1	1.0079	Nonmetals	1766	Henry Cavendish
Indium	In	49	114.818	Other metals	1863	Ferdinand Reich and Hieronymus Richter
Iodine	I	53	126.9045	Halogens	1811	Bernard Courtois
Iridium	Ir	77	192.217	Transition metals	1804	Smithson Tennant
Iron	Fe	26	55.845	Transition metals	prehistoric	unknown
Krypton	Kr	36	83.798	Noble gases	1898	William Ramsay and Morris Travers
Lanthanum	La	57	138.9055	Lanthanide series	1839	Carl Mosander
Lawrencium	Lr	103	(260)	Transition metals	1961	Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh, and Robert Latimer
Lead	Pb	82	207.2	Other metals	prehistoric	unknown
Lithium	Li	3	6.941	Alkali metals	1817	Johan Arfwedson
Lutetium	Lu	71	174.967	Transition metals	1907	Georges Urbain and Carl von Welsbach, independently of each other
Magnesium	Mg	12	24.3051	Alkaline earth metals	1755	Joseph Black (oxide isolated by Humphry Davy 1808; pure form isolated by Antoine-Alexandre-Brutus Bussy 1828)
Manganese	Mn	25	54.938	Transition metals	1774	Johann Gottlieb Gahn
Meitnerium	Mt	109	(268)	Transition metals	1982	Peter Armbruster and coworkers
Mendelevium	Md	101	(258)	Actinide series	1955	Albert Ghiorso, Bernard G. Harvey, Gregory Choppin, Stanley Thompson, and Glenn Seaborg
Mercury	Hg	80	200.59	Transition metals	prehistoric	unknown
Molybdenum	Mo	42	95.94	Transition metals	1781	named by Karl Scheele (isolated by Peter Jacob Hjelm 1782)
Neodymium	Nd	60	144.24	Lanthanide series	1885	Carl von Welsbach
Neon	Ne	10	20.1798	Noble gases	1898	William Ramsay and Morris Travers
Neptunium	Np	93	(237)	Actinide series	1940	Edwin McMillan and Philip Abelson
Nickel	Ni	28	58.6934	Transition metals	1751	Axel Cronstedt
Niobium	Nb	41	92.9064	Transition metals	1801	Charles Hatchett
Nitrogen	N	7	14.0067	Nonmetals	1772	Daniel Rutherford
Nobelium	No	102	(259)	Actinide series	1958	Albert Ghiorso, Torbjørn Sikkeland, J. R. Walton, and Glenn Seaborg
Osmium	Os	76	190.23	Transition metals	1804	Smithson Tennant
Oxygen	O	8	15.9994	Nonmetals	1774	Joseph Priestley and Karl Scheele, independently of each other
Palladium	Pd	46	106.42	Transition metals	1804	William Wollaston
Phosphorus	P	15	30.9738	Nonmetals	1674	Hennig Brand
Platinum	Pt	78	195.08	Transition metals	1557	Julius Scaliger
Plutonium	Pu	94	(244)	Actinide series	1940	Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl
Polonium	Po	84	(209)	Other metals	1898	Marie and Pierre Curie
Potassium	K	19	39.0983	Alkali metals	1807	Humphry Davy
Praseodymium	Pr	59	140.908	Lanthanide series	1885	Carl von Welsbach
Promethium	Pm	61	(145)	Lanthanide series	1945	J. A. Marinsky, Lawrence Glendenin, and Charles Coryell
Protactinium	Pa	91	231.036	Actinide series	1913	Kasimir Fajans and O. Göhring
Radium	Ra	88	(226)	Alkaline earth metals	1898	Marie Curie
Radon	Rn	86	(222)	Noble gases	1900	Friedrich Dorn
Rhenium	Re	75	186.207	Transition metals	1925	Walter Noddack, Ida Tacke, and Otto Berg
Rhodium	Rh	45	102.9055	Transition metals	1804	William Wollaston
Rubidium	Rb	37	85.4678	Alkali metals	1861	Robert Bunsen and Gustav Kirchhoff
Ruthenium	Ru	44	101.07	Transition metals	1827	G. W. Osann (isolated by Karl Klaus 1844)
Rutherfordium	Rf	104	(261)	Transition metals	1969	claimed by U.S. scientist Albert Ghiorso and coworkers (disputed by Soviet workers)
Samarium	Sm	62	150.36	Lanthanide series	1879	Paul Lecoq de Boisbaudran
Scandium	Sc	21	44.9559	Transition metals	1876	Lars Nilson
Seaborgium	Sg	106	(266)	Transition metals	1974	claimed by Georgii Flerov and coworkers, and independently by Albert Ghiorso and coworkers
Selenium	Se	34	78.96	Nonmetals	1817	Jöns Berzelius
Silicon	Si	14	28.0855	Nonmetals	1823	Johan Arfwedson
Silver	Ag	47	107.8682	Transition metals	prehistoric	unknown
Sodium	Na	11	22.9898	Alkali metals	1807	Humphry Davy
Strontium	Sr	38	87.62	Alkaline earth metals	1808	Humphry Davy
Sulfur	S	16	32.067	Nonmetals	prehistoric	unknown
Tantalum	Ta	73	180.948	Transition metals	1802	Anders Ekeberg
Technetium	Tc	43	(98)	Transition metals	1937	Carlo Perrier and Emilio Segrè
Tellurium	Te	52	127.60	Nonmetals	1782	Franz Müller
Terbium	Tb	65	158.9253	Lanthanide series	1843	Carl Mosander
Thallium	Tl	81	204.3833	Other metals	1861	William Crookes (isolated by William Crookes and Claude August Lamy, independently of each other, in 1862)
Thorium	Th	90	232.0381	Actinide series	1828	Jöns Berzelius
Thulium	Tm	69	168.9342	Lanthanide series	1879	Per Cleve
Tin	Sn	50	118.711	Other metals	prehistoric	unknown
Titanium	Ti	22	47.867	Transition metals	1790	William Gregor
Tungsten	W	74	183.84	Transition metals	1783	isolated by Juan José Elhuyar and Fausto Elhuyar
Ununbium	Uub	112	(277)	Transition metals	1996	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
Ununhexium	Uuh	116	(292)	Other metals	2000	team at the Joint Institute for Nuclear Research, Dubna, Russia
Ununquadium	Uuq	114	(285)	Other metals	1998	team at the Joint Institute for Nuclear Research, Dubna, Russia
Roentgenium	Rg	111	(272)	Transition metals	1994	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
Uranium	U	92	238.0289	Actinide series	1789	Martin Klaproth (isolated by Eugène Péligot 1841)
Vanadium	V	23	50.9415	Transition metals	1801	Andrés del Rio (disputed), or Nils Sefström 1830
Xenon	Xe	54	131.29	Noble gases	1898	William Ramsay and Morris Travers
Ytterbium	Yb	70	173.04	Lanthanide series	1878	Jean Charles de Marignac
Yttrium	Y	39	88.906	Transition metals	1794	Johan Gadolin
Zinc	Zn	30	65.409	Transition metals	prehistoric	unknown
Zirconium	Zr	40	91.224	Transition metals	1789	Martin Klaproth

Elements Sorted by Atomic Number

Atomic Number

Name

Symbol

Atomic Weight

Group

Date Discovered

Discovered By

1	Hydrogen	H	1.0079	Nonmetals	1766	Henry Cavendish
2	Helium	He	4.0026	Noble gases	1868	Pierre Janssen
3	Lithium	Li	6.941	Alkali metals	1817	Johan Arfwedson
4	Beryllium	Be	9.0122	Alkaline earth metals	1798	Louis-Nicolas Vauquelin (isolated by Friedrich Wöhler and Antoine-Alexandre-Brutus Bussy 1828)
5	Boron	B	10.81	Nonmetals	1808	Humphry Davy, and independently by Joseph Gay-Lussac and Louis-Jacques Thénard
6	Carbon	C	12.011	Nonmetals	prehistoric	unknown
7	Nitrogen	N	14.0067	Nonmetals	1772	Daniel Rutherford
8	Oxygen	O	15.9994	Nonmetals	1774	Joseph Priestley and Karl Scheele, independently of each other
9	Fluorine	F	18.9984	Halogens	1771	Karl Scheele (isolated by Henri Moissan 1886)
10	Neon	Ne	20.1798	Noble gases	1898	William Ramsay and Morris Travers
11	Sodium	Na	22.9898	Alkali metals	1807	Humphry Davy
12	Magnesium	Mg	24.3051	Alkaline earth metals	1755	Joseph Black (oxide isolated by Humphry Davy 1808; pure form isolated by Antoine-Alexandre-Brutus Bussy 1828)
13	Aluminum	Al	26.9815	Other metals	1824	Hans Oersted (also attributed to Friedrich Wöhler 1827)
14	Silicon	Si	28.0855	Nonmetals	1823	Johan Arfwedson
15	Phosphorus	P	30.9738	Nonmetals	1674	Hennig Brand
16	Sulfur	S	32.067	Nonmetals	prehistoric	unknown
17	Chlorine	Cl	35.4528	Halogens	1774	Karl Scheele
18	Argon	Ar	39.948	Noble gases	1894	John Rayleigh and William Ramsay
19	Potassium	K	39.0983	Alkali metals	1807	Humphry Davy
20	Calcium	Ca	40.078	Alkaline earth metals	1808	Humphry Davy
21	Scandium	Sc	44.9559	Transition metals	1876	Lars Nilson
22	Titanium	Ti	47.867	Transition metals	1790	William Gregor
23	Vanadium	V	50.9415	Transition metals	1801	Andrés del Rio (disputed), or Nils Sefström 1830
24	Chromium	Cr	51.9962	Transition metals	1797	Louis-Nicolas Vauquelin
25	Manganese	Mn	54.938	Transition metals	1774	Johann Gottlieb Gahn
26	Iron	Fe	55.845	Transition metals	prehistoric	unknown
27	Cobalt	Co	58.9332	Transition metals	1730	Georg Brandt
28	Nickel	Ni	58.6934	Transition metals	1751	Axel Cronstedt
29	Copper	Cu	63.546	Transition metals	prehistoric	unknown
30	Zinc	Zn	65.409	Transition metals	prehistoric	unknown
31	Gallium	Ga	69.723	Other metals	1875	Paul Lecoq de Boisbaudran
32	Germanium	Ge	72.61	Other metals	1886	Clemens Winkler
33	Arsenic	As	74.9216	Nonmetals	prehistoric	unknown
34	Selenium	Se	78.96	Nonmetals	1817	Jöns Berzelius
35	Bromine	Br	79.904	Halogens	1826	Antoine-Jérôme Balard
36	Krypton	Kr	83.798	Noble gases	1898	William Ramsay and Morris Travers
37	Rubidium	Rb	85.4678	Alkali metals	1861	Robert Bunsen and Gustav Kirchhoff
38	Strontium	Sr	87.62	Alkaline earth metals	1808	Humphry Davy
39	Yttrium	Y	88.906	Transition metals	1794	Johan Gadolin
40	Zirconium	Zr	91.224	Transition metals	1789	Martin Klaproth
41	Niobium	Nb	92.9064	Transition metals	1801	Charles Hatchett
42	Molybdenum	Mo	95.94	Transition metals	1781	named by Karl Scheele (isolated by Peter Jacob Hjelm 1782)
43	Technetium	Tc	(98)	Transition metals	1937	Carlo Perrier and Emilio Segrè
44	Ruthenium	Ru	101.07	Transition metals	1827	G. W. Osann (isolated by Karl Klaus 1844)
45	Rhodium	Rh	102.9055	Transition metals	1804	William Wollaston
46	Palladium	Pd	106.42	Transition metals	1804	William Wollaston
47	Silver	Ag	107.8682	Transition metals	prehistoric	unknown
48	Cadmium	Cd	112.412	Transition metals	1817	Friedrich Strohmeyer
49	Indium	In	114.818	Other metals	1863	Ferdinand Reich and Hieronymus Richter
50	Tin	Sn	118.711	Other metals	prehistoric	unknown
51	Antimony	Sb	121.760	Other metals	prehistoric	unknown
52	Tellurium	Te	127.60	Nonmetals	1782	Franz Müller
53	Iodine	I	126.9045	Halogens	1811	Bernard Courtois
54	Xenon	Xe	131.29	Noble gases	1898	William Ramsay and Morris Travers
55	Cesium	Cs	132.9054	Alkali metals	1860	Robert Bunsen and Gustav Kirchhoff
56	Barium	Ba	137.328	Alkaline earth metals	1808	Humphry Davy
57	Lanthanum	La	138.9055	Lanthanide series	1839	Carl Mosander
58	Cerium	Ce	140.115	Lanthanide series	1804	Jöns Berzelius and Wilhelm Hisinger, and independently by Martin Klaproth
59	Praseodymium	Pr	140.908	Lanthanide series	1885	Carl von Welsbach
60	Neodymium	Nd	144.24	Lanthanide series	1885	Carl von Welsbach
61	Promethium	Pm	(145)	Lanthanide series	1945	J. A. Marinsky, Lawrence Glendenin, and Charles Coryell
62	Samarium	Sm	150.36	Lanthanide series	1879	Paul Lecoq de Boisbaudran
63	Europium	Eu	151.966	Lanthanide series	1901	Eugène Demarçay
64	Gadolinium	Gd	157.25	Lanthanide series	1886	Paul Lecoq de Boisbaudran
65	Terbium	Tb	158.9253	Lanthanide series	1843	Carl Mosander
66	Dysprosium	Dy	162.500	Lanthanide series	1886	Paul Lecoq de Boisbaudran
67	Holmium	Ho	164.9303	Lanthanide series	1879	Per Cleve
68	Erbium	Er	167.26	Lanthanide series	1843	Carl Mosander
69	Thulium	Tm	168.9342	Lanthanide series	1879	Per Cleve
70	Ytterbium	Yb	173.04	Lanthanide series	1878	Jean Charles de Marignac
71	Lutetium	Lu	174.967	Transition metals	1907	Georges Urbain and Carl von Welsbach, independently of each other
72	Hafnium	Hf	178.49	Transition metals	1913	Dirk Coster and Georg von Hevesy
73	Tantalum	Ta	180.948	Transition metals	1802	Anders Ekeberg
74	Tungsten	W	183.84	Transition metals	1783	isolated by Juan José Elhuyar and Fausto Elhuyar
75	Rhenium	Re	186.207	Transition metals	1925	Walter Noddack, Ida Tacke, and Otto Berg
76	Osmium	Os	190.23	Transition metals	1804	Smithson Tennant
77	Iridium	Ir	192.217	Transition metals	1804	Smithson Tennant
78	Platinum	Pt	195.08	Transition metals	1557	Julius Scaliger
79	Gold	Au	196.9665	Transition metals	prehistoric	unknown
80	Mercury	Hg	200.59	Transition metals	prehistoric	unknown
81	Thallium	Tl	204.3833	Other metals	1861	William Crookes (isolated by William Crookes and Claude August Lamy, independently of each other, in 1862)
82	Lead	Pb	207.2	Other metals	prehistoric	unknown
83	Bismuth	Bi	208.9804	Other metals	prehistoric	unknown
84	Polonium	Po	(209)	Other metals	1898	Marie and Pierre Curie
85	Astatine	At	(210)	Halogens	1940	Dale R. Corson, K. R. MacKenzie, and Emilio Segrè
86	Radon	Rn	(222)	Noble gases	1900	Friedrich Dorn
87	Francium	Fr	(223)	Alkali metals	1939	Marguérite Perey
88	Radium	Ra	(226)	Alkaline earth metals	1898	Marie Curie
89	Actinium	Ac	(227)	Actinide series	1899	André Debierne
90	Thorium	Th	232.0381	Actinide series	1828	Jöns Berzelius
91	Protactinium	Pa	231.036	Actinide series	1913	Kasimir Fajans and O. Göhring
92	Uranium	U	238.0289	Actinide series	1789	Martin Klaproth (isolated by Eugène Péligot 1841)
93	Neptunium	Np	(237)	Actinide series	1940	Edwin McMillan and Philip Abelson
94	Plutonium	Pu	(244)	Actinide series	1940	Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl
95	Americium	Am	243	Actinide series	1944	Glenn Seaborg, Ralph James, Leon Morgan, and Albert Ghiorso
96	Curium	Cm	(247)	Actinide series	1944	Glenn Seaborg, Ralph James, and Albert Ghiorso
97	Berkelium	Bk	(247)	Actinide series	1949	Glenn Seaborg, Stanley Thompson, and Albert Ghiorso
98	Californium	Cf	(251)	Actinide series	1950	Glenn Seaborg, Stanley Thompson, Kenneth Street, Jr., and Albert Ghiorso
99	Einsteinium	Es	(252)	Actinide series	1952	Albert Ghiorso and coworkers
100	Fermium	Fm	(257)	Actinide series	1955	Albert Ghiorso and coworkers
101	Mendelevium	Md	(258)	Actinide series	1955	Albert Ghiorso, Bernard G. Harvey, Gregory Choppin, Stanley Thompson, and Glenn Seaborg
102	Nobelium	No	(259)	Actinide series	1958	Albert Ghiorso, Torbjørn Sikkeland, J. R. Walton, and Glenn Seaborg
103	Lawrencium	Lr	(260)	Transition metals	1961	Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh, and Robert Latimer
104	Rutherfordium	Rf	(261)	Transition metals	1969	claimed by U.S. scientist Albert Ghiorso and coworkers (disputed by Soviet workers)
105	Dubnium	Db	(262)	Transition metals	1970	claimed by Albert Ghiorso and coworkers (disputed by Soviet workers)
106	Seaborgium	Sg	(266)	Transition metals	1974	claimed by Georgii Flerov and coworkers, and independently by Albert Ghiorso and coworkers
107	Bohrium	Bh	(262)	Transition metals	1976	Georgii Flerov and Yuri Oganessian (confirmed by German scientist Peter Armbruster and coworkers)
108	Hassium	Hs	(263)	Transition metals	1984	Peter Armbruster and coworkers
109	Meitnerium	Mt	(268)	Transition metals	1982	Peter Armbruster and coworkers
110	Darmstadtium	Ds	(271)	Transition metals	1994	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
111	Roentgenium	Rg	(272)	Transition metals	1994	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
112	Ununbium	Uub	(277)	Transition metals	1996	team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
114	Ununquadium	Uuq	(285)	Other metals	1998	team at the Joint Institute for Nuclear Research, Dubna, Russia
116	Ununhexium	Uuh	(292)	Other metals	2000	team at the Joint Institute for Nuclear Research, Dubna, Russia

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