Cobalt

27

Co

58.933195(

  • Name: Cobalt
  • Symbol: Co
  • Atomic number: 27
  • Atomic weight: 58.933195(
  • CAS Registry ID: 7440-48-4
  • Group name: (none)
  • Period number: 4
  • Block: d-block
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Description

Cobalt is one of the transition metals with ferromagnetic properties; it is a metal with a metallic gray color in its natural solid state. Cobalt has an atomic weight of 58.933195, a melting point of 2723 °F, and a boiling point of 5301 °F. Some common uses of cobalt include: as a component in metallic alloys for high speed steels, as a component in super-alloys for turbine aircraft engine parts, as a component in magnetic recording devices, and as a component in electroplating.

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Isolation

Cobalt is never found freely in nature, and there are isolation procedures that are used to isolate cobalt from mineral ores.

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Cobalt is generally isolated from byproducts in copper, nickel, and lead production. The major ores that contain cobalt is cobaltite, erythrite, glaucodot, and skutterudite. In the process which results in isolation of cobalt, the mineral ore is first heated to form a mixture of metals and their metal oxides. The addition of sulphuric acid to the mixture causes copper to come out of the mixture as a residue, and iron, cobalt, and nickel form their sulphates. The addition of sodium hypochlorite to the resulting mixture causes cobalt to precipitate out in a trihydroxide form. The trihydroxide of cobalt is then heated to form cobalt oxide and water. In the final step of isolation, the cobalt is reduced with carbon in the form of charcoal resulting in pure cobalt and carbon dioxide.

The isolation procedures of cobalt are very rarely performed in a laboratory as the process is highly inefficient and pure cobalt is available commercially.


General
Name Cobalt
Symbol Co
Number 27
Chemical series transition metals
Group 9
Period 4
Block d
Appearance metallic with gray tinge
Standard atomic weight 58.933195(5) g·mol−1
Electron configuration [Ar] 3d7 4s2
Electrons per shell 2, 8, 15, 2
Atomic properties
Crystal structure hexagonal
Oxidation states 2, 3 (amphoteric oxide)
Electronegativity 1.88 (Pauling scale)
Ionization energies 1st: 760.4 kJ·mol−1
(more) 2nd: 1648 kJ·mol−1
(more) 3rd: 3232 kJ·mol−1
Atomic radius 135 pm
Atomic radius (calc.) 152 pm
Covalent radius 126 pm
Van der Waals radius
Physical properties
Phase
Density (near r.t.) 8.90 g·cm−3
Liquid density at m.p. 7.75 g·cm−3
Melting point 1768 K (1495 °C, 2723 °F)
Boiling point 3200 K (2927 °C, 5301 °F)
Critical point
Heat of fusion 16.06 kJ·mol−1
Heat of vaporization 377 kJ·mol−1
Heat capacity (25 °C) 24.81 J·mol−1·K−1
Miscellaneous
Magnetic ordering ferromagnetic
Electrical resistivity (20 °C) 62.4 nΩ·m
Thermal conductivity (300 K) 100 W·m−1·K−1
Thermal expansion (25 °C) 13.0 µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 4720 m/s
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 700 MPa
CAS registry number 7440-48-4

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