Cobalt, Co 27 Cobalt Pronunciation / ( ) listen  Appearance hard lustrous bluish gray metal Standard atomic weight A r, std(Co) 58.933 194(3)  Cobalt in the periodic table Atomic number ( Z) 27 Group group 9 Period period 4 Block d-block Element category Transition metal Electron configuration [ ] 3d Ar 7 4s 2 Electrons per shell 2, 8, 15, 2 Physical properties Phase at STP solid Melting point 1768 (1495 °C, 2723 °F) K Boiling point 3200 K (2927 °C, 5301 °F) Density (near r.t.) 8.90 g/cm 3 when liquid (at m.p.) 8.86 g/cm 3 Heat of fusion 16.06 kJ/mol Heat of vaporization 377 kJ/mol Molar heat capacity 24.81 J/(mol·K) Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1790 1960 2165 2423 2755 3198 Atomic properties Oxidation states −3, −1, 0, +1, , +2 , +4, +5 +3 (an  oxide) amphoteric Electronegativity Pauling scale: 1.88 Ionization energies 1st: 760.4 kJ/mol 2nd: 1648 kJ/mol 3rd: 3232 kJ/mol ( ) more Atomic radius empirical: 125 pm Covalent radius Low spin: 126±3 pm High spin: 150±7 pm of cobalt Spectral lines Other properties Natural occurrence primordial Crystal structure (hcp) hexagonal close-packed Speed of sound thin rod 4720 m/s (at 20 °C) Thermal expansion 13.0 µm/(m·K) (at 25 °C) Thermal conductivity 100 W/(m·K) Electrical resistivity 62.4 nΩ·m (at 20 °C) Magnetic ordering ferromagnetic Young's modulus 209 GPa Shear modulus 75 GPa Bulk modulus 180 GPa Poisson ratio 0.31 Mohs hardness 5.0 Vickers hardness 1043 MPa Brinell hardness 470–3000 MPa CAS Number 7440-48-4 History and first isolation Discovery (1735) Georg Brandt Main isotopes of cobalt | Cobalt is a with the chemical element symbol Co and atomic number 27. Like nickel, cobalt is found in the Earth's crust only in chemically combined form, save for small deposits found in alloys of natural . The free element, produced by reductive meteoric iron , is a hard, lustrous, silver-gray smelting . metal
Cobalt-based blue pigments (
) have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was later thought to be due to the known metal cobalt blue . Miners had long used the name bismuth (German for ore kobold goblin ore) for some of the blue-pigment-producing ; they were so named because they were poor in known metals, and gave poisonous minerals -containing fumes when smelted. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the arsenic kobold.
Today, some cobalt is produced specifically from one of a number of metallic-lustered ores, such as
(CoAsS). The element is, however, more usually produced as a by-product of cobaltite and copper mining. nickel in the The copper belt (DRC) and Democratic Republic of the Congo yields most of the global cobalt production. World production in 2016 was 116,000 tonnes (according to Zambia ), and the DRC alone accounted for more than 50%. Natural Resources Canada 
Cobalt is primarily used in
, and in the manufacture of lithium-ion batteries , wear-resistant and high-strength magnetic . The compounds cobalt silicate and alloys (CoAl cobalt(II) aluminate 2O 4, cobalt blue) give a distinctive deep blue color to , glass , ceramics , inks and paints . Cobalt occurs naturally as only one stable varnishes , cobalt-59. isotope is a commercially important radioisotope, used as a Cobalt-60 and for the production of high-energy radioactive tracer . gamma rays
Cobalt is the active center of a group of
called coenzymes . cobalamins , the best-known example of the type, is an essential Vitamin B 12 for all animals. Cobalt in inorganic form is also a vitamin for micronutrient , bacteria , and algae . fungi
A block of
refined cobalt (99.9% purity) cut from a large plate
Cobalt is a
metal with a ferromagnetic of 8.9. The specific gravity is 1,115 °C (2,039 °F) Curie temperature and the magnetic moment is 1.6–1.7  per Bohr magnetons . atom Cobalt has a  two-thirds that of relative permeability . iron  cobalt occurs as two Metallic : crystallographic structures and hcp . The ideal transition temperature between the hcp and fcc structures is 450 °C (842 °F), but in practice the energy difference between them is so small that random intergrowth of the two is common. fcc  
Cobalt is a weakly reducing metal that is protected from oxidation by a
passivating film. It is attacked by oxide and halogens . Heating in sulfur produces oxygen which loses oxygen at 900 °C (1,650 °F) to give the Co 3O 4 CoO. monoxide The metal reacts with  ( fluorine ) at 520 K to give F 2 ; with CoF 3 ( chlorine ), Cl 2 ( bromine ) and Br 2 ( iodine ), producing equivalent binary I 2 . It does not react with halides ( hydrogen gas ) or H 2 ( nitrogen gas ) even when heated, but it does react with N 2 , boron , carbon , phosphorus and sulfur. arsenic At ordinary temperatures, it reacts slowly with  , and very slowly with moist, but not with dry, air.