Symbol	Co
Atomic number	27
Group	9 (Cobalt group)
Period	4
Block	d
Classification	Transition Metal

Appearance	Hard lustrous gray metal
Color	Gray

Number of protons	27 p+
Number of neutrons	32 n0
Number of electrons	27 e-

From Wikipedia, the free encyclopediaCobalt 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.

Phase at STP	Solid
Density	8.9 g/cm3
Atomic weight	58.9332 u

Melting point	1768 K 1494.85 °C 2722.73 °F
Boiling point	3200 K 2926.85 °C 5300.33 °F
Heat of vaporization	373.3 kJ/mol

Electronegativity (Pauling Scale)	1.88
Electron affinity	63.898 kJ/mol
Oxidation states	−3, −1, 0, +1, +2, +3, +4, +5 (an amphoteric oxide)
Ionization energies	760.4 kJ/mol 1648 kJ/mol 3232 kJ/mol 4950 kJ/mol 7670 kJ/mol 9840 kJ/mol 12440 kJ/mol 15230 kJ/mol 17959 kJ/mol 26570 kJ/mol 29400 kJ/mol 32400 kJ/mol 36600 kJ/mol 39700 kJ/mol 42800 kJ/mol 49396 kJ/mol 52737 kJ/mol 134810 kJ/mol 145170 kJ/mol 154700 kJ/mol 167400 kJ/mol 178100 kJ/mol 189300 kJ/mol 204500 kJ/mol 214100 kJ/mol 920870 kJ/mol 966023 kJ/mol

Electron configuration Shorthand configuration	[Ar] 3d7 4s2
Electron configuration Full configuration	1s2 2s2 2p6 3s2 3p6 3d7 4s2
Electron configuration chart	1s2 2s2 2p6 3s2 3p6 3d7 4s2
Electrons per shell	2, 8, 15, 2
Valence electrons	2 or 9
Valency electrons	2,3
Bohr model	Figure: Shell diagram of Cobalt (Co) atom.
Orbital Diagram	1s 2s 2p 3s 3p 3d 4s

Discovery and first isolation

Georg Brandt (1735)

Discovery of cobalt Cobalt has been used to color glass since the Bronze Age. The word cobalt is derived from the German kobalt, from kobold meaning "goblin", a superstitious term used for the ore of cobalt by miners. The first attempts to smelt those ores for copper or silver failed, yielding simply powder (cobalt(II) oxide) instead. Because the primary ores of cobalt always contain arsenic, smelting the ore oxidized the arsenic into the highly toxic and volatile arsenic oxide, adding to the notoriety of the ore. Swedish chemist Georg Brandt (1694–1768) is credited with discovering cobalt circa 1735, showing it to be a previously unknown element, distinct from bismuth and other traditional metals. Brandt called it a new "semi-metal". He showed that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to the bismuth found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period. All other known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers.

CAS Number	7440-48-4
ChemSpider ID	94547
EC number	231-158-0
PubChem CID Number	104730