The chemical symbol for Cobalt is Co and its atomic number is 27.
We find it listed in the periodic table in Group 9 and period 4, and block d.
Cobalt belongs to the family of transition metals such as for example the Silver, the Bohrium, cadmium, ...
This element is stable.
Atomic number (Z) 27
Group, block group 9, d-block
Period: period 4
Element category: transition metal
Standard atomic weight (±) (Ar) 58.933194(4)
Electron configuration [Ar] 3d7 4s2
per shell: 2, 8, 15, 2
Physical properties
Color: metallic gray
Phase: solid
Melting point: 1768 K (1495 °C, 2723 °F)
Boiling point: 3200 K (2927 °C, 5301 °F)
Density near r.t. : 8.90 g/cm3
when liquid, at m.p. 8.86 g/cm3
Heat of fusion: 16.06 kJ/mol
Heat of vaporization: 377 kJ/mol
Molar heat capacity: 24.81 J/(mol·K)
Atomic properties
Oxidation states: −3, −1, +1, +2, +3, +4, +5 (an amphoteric oxide)
Electronegativity: Pauling scale: 1.88
Ionization energies 1st: 760.4 kJ/mol
2nd: 1648 kJ/mol
3rd: 3232 kJ/mol
Atomic radius empirical: 125 pm
Covalent radius: Low spin: 126±3 pm
High spin: 150±7 pm
Element Crystal structure: 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