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Cobalt Co (Element 27) of Periodic Table

Cobalt Co (Element 27) of Periodic Table

27 Co (Cobalt)
Cobalt is a silver-white, hard, lustrous, brittle element, and resembling iron and nickel in appearance.
It can be magnetized ( Like Iron).

Cobalt tends to exist as a mixture of two allotropes over a wide temperature range.
Its physical properties is similar to iron and nickel.
The element is active chemically, and forming many compounds.
Cobalt is stable in air and unaffected by water, but is slowly attacked by dilute acids.

Cobalt element

Pure (99.8%) Cobalt Metal


CAS Number: CAS7440-48-4
CID Number:  CID104730
DOT Hazard Class:  4.1
DOT Number:  3089
RTECS Number:  RTECSGF8750000

Basic Properties of Cobalt

Appearance:  Hard lustrous bluish gray metal
Mass Number:  59
Standard Atomic weight: 58.933  g/mol
Atomic number (Z):  27
Electrons: 27
Protons:  27
Neutrons:  32
Period:  4
Group:  9
Block:  d
Element category:  Transition metal
Electrons per shell:  K2, L8, M15, N2
Electron configuration:  1s22s22p63s23p63d74s2 

Cobalt electron configuration

Cobalt Electron Configuration

Thermal Properties of Cobalt

Phase:  Solid
Melting point:  1768 K (1495 oC, 2723 oF)
Boiling point:   3200 K (2927 oC, 5301 oF)
Debye temperature:  385 K (111.85 oC, 233.33 oF)
Fusion heat:   16.06 kJ/mol
Vaporization heat:  377 kJ/mol
Specific heat:  421 J/(kg K)
Molar heat capacity:  24.81 J/(mol.K)
Thermal expansion:  13 μm/(m∙K)
Thermal conductivity:  100 W/(m∙K)

Electrical properties of Cobalt

Electrical conductivity:  17×106 S/m
Electrical resistivity:  62.4 nΩ∙m
A Electrical type:  Conductor

Magnetic Properties of Cobalt

A  Magnetic type:  ferromagnetic
Curie point:  1394 K (1120.85 oC, 2049.53 oF) (above which Ferromagnetism vanishes)
Magnetic susceptibility (xmol):  +1860×10-6 cm3/mol

Physical Properties of Cobalt

Density:  8.90 g/cm3 (In solid)  8.86 g/cm3 (In Liquid at M.P)
Molar volume:  0.00000662 m3/mol
Young’s modulus:  209 GPa
Shear modulus:  75 GPa
Mohs Hardness:  5.0
Bulk modulus:  180 GPa
Poisson ratio:  0.31
Vicker hardness:  1043 MPa
Brinell hardness:  470-3000 MPa
Sound Speed:  4720 m/s

Atomic Properties of Cobalt 

Oxidation states:  -3, -1, +1, +2, +3, +4, +5
Valence Electrons:  3d7 4s2
Ion charge:  Co2+ Co3+
The ionization potential of an atom:  7.81
Ionization energies:  1st: 760.4 kJ.mol 2nd: 1648 kJ/mol 3rd: 3232 kJ/mol
Ionic radius:   74.5 pm
Atomic radius:  empirical: 125 pm
Van der Waals:  192 Pm
Covalent radius:  126±3 pm (Low spin), 150±7 pm (High spin)
Filling Orbital:  3d7
Crystal structure:  Hexagonal close packed
Lattice angles:  π/2, π/2, 2π/3
Lattice constant:  250.5, 250.5, 408.9 pm
Grid parameters:  a=2.505 Å c=4.089 Å
Attitude c/a:  1.632
Space Group Name:  P63/mmc
Space Group Number:  194

Hexagonal Close Packed

Hexagonal Close Packed (HCP)

Reactivity of Cobalt

Electronegativity:  pauling scale: 1.88
Valence:  +4
Electron affinity:  63.7 kJ/mol

Nuclear Properties of Cobalt

Half Life:  Stable (Infinity) 
Lifetime:  Stable (Infinity)
Quantum Number:  4F9/2
Neutron cross section (Brans):  37.2
Neutron Mass Absorption:  0.021
Isotopes:   56Co 57Co 58Co 59Co 60Co

Isotope Abundance (%) Atomic Mass g/mol Half Life (t1/2)
56Co Syn 77.27 d
57Co Syn 271.79 d
58Co Syn 70.86 d
59Co 100 58.933 Stable
60Co Syn 5.2714 y

Chemical Reactions of Cobalt

It does not react readily with air. However, on heating the oxide Co3O4 is formed:
3Co (s) + 4 O2 (g) → 2 Co3O4 (s)
If the reaction is carried out above 900°C, the cobalt(II) oxide CoO is formed:
2 Co (s) + O2 (g) → 2 CoO (s)
Cobalt does not react with Nitrogen.

Water has little effect upon cobalt metal, The reaction between red hot cobalt metal and steam produces cobalt(II) oxide, CoO.
2 Co (s) + O2 (g) → 2 CoO (s)

The metal reacts with bromine, and forming:
Co (s) + Br2 (I) → CoBr2 (s) [green] (Cobalt (II) bromide)
The metal also reacts with chloride and iodide, but as a synthetic pathway other reactions are used:
Co (s) + Cl2 (g) → CoCl2 (s) [blue] (Cobalt (II) chloride)
Co (s) + I2 (s) → CoL2 (s) [blue-black] (Cobalt (II) Iodide)

Co(II) forms complexes with Cl: 
[Co(H2O)6]2+ (aq) + 4 Cl (aq) → [CoCl4]2- (aq) + 6 H2O (I)

Cobalt metal dissolves slowly in dilute sulphuric acid, and forming aquated solutions containing the Co(II) ion together with hydrogen gas, he actual occurrence of Co(II) in aqueous solution is as the complex ion [Co(OH2)6]2+.
Co (s) + H2SO4 (aq) → Co2+ (aq) + SO42- (aq) + H2 (g)
Co(II) reacts with HCl(aq) under strongly acidic conditions, and forming tetrahedral chloro complexes:
[Co(H2O)6]2+ (aq) + 4 Cl (aq) → [CoCl4]2- (aq) [deep blue] + 6 H2O (I)

Cobalt History

Naming:  German: kobalt or kobold (evil spirit); Greek: cobalos (mines).
Discovery and first isolation: Georg Brandt (1735) in Stockholm Sweden

Cobalt Uses

Cobalt can be magnetized (like iron), so it is used to make magnets, It is alloyed with iron, nickel and other metals to make Alnico (Al, Ni, Co), an alloy of unusual magnetic strength with many important uses.

Stellite alloys (containing cobalt, chromium, and tungsten) are used for high-speed, heavy-duty, high temperature cutting tools, and dies.
Other alloys of cobalt are used in magnetic steels, stainless steels, and in jet turbine and gas turbine generators (where high-temperature strength is important).

The metal is used in electroplating because of its attractive appearance, hardness and resistance to corrosion or oxidation.
Cobalt salts have been used for centuries to produce brilliant and permanent blue colours in paint, porcelain (a white vitrified translucent ceramic), glass, tiles, pottery and enamels.
Its rich blue colour is also known as Sèvres blue and Thénard blue.

A aqueous solution of the cobalt chloride (CoCl2) with added glycerol is almost colourless (very pale pink) , and it was used to write secret massages, It is also popular as invisible ink.
It would read by simply heated the paper and the hidden writing appeared, Because the heating drove off the water and glycerol molecules that surround the cobalt, and chloride ions moved in to take their place, giving dark blue CoCl42- ions.

Cobalt carefully used in the form of the chloride (CoCl2), sulfate (CoSO4), acetate (Co(CH3COO)2) , or nitrate (Co(NO3)2) has been found effective in correcting a certain mineral deficiency disease in animals.

Biological role of Cobalt 

Cobalt is essential to the metabolism of all animals, and It forms part of the active site of vitamin B12.
The amount we need is very small, and an uptake of 0.20 mg/kg a day (body contains only about 1 milligram) is recommended because they have no other source of vitamin B12.
In large doses of cobalt is carcinogenic.

Cobalt-60 is a radioactive isotope, and It is an important source of gamma-rays.
It is widely used in cancer treatment, to irradiate food to preserve it, and as a tracer and for radiotherapy.

cobalt 60

cobalt 60 In Cancer Therapy Machine

Abundance of Cobalt

Cobalt is found in the minerals Cobaltite (CoAsS), Skutterudite (CoAs3)and Erythrite (Co3(AsO4)2·8H2O), and is often associated with nickel, silver, lead, copper, and iron ores, from which it is formed as a by-product of refining.
It is also present in meteorites.

The U.S. Geological Survey has announced that the bottom of the north central Pacific Ocean may have a huge reserve of several transition metals (including many tonnes of cobalt) deposits on the floors of the deepest in water close to the the Hawaiian Islands and other U.S. Pacific territories.

Annual world wide production is around 2,00,000 metric tons, and World wide Reserve is around 7,100,000 metric tons.
0.0003% (In Universe)
0.059% (In Meteorites)
0.0004% (In Sun)
0.003% (In Earth’s Crust)
8×10-9% (In Oceans)
2×10-6% (In Humans)

Cobaltite mineral

Cobaltite Mineral

Skutterudite and Nickeline

Skutterudite and Nickeline Mineral

Erythrite mineral

Erythrite Mineral

World’s Top 3 producers of Cobalt

1) DRC
2) China
3) Zambia

World’s Top 3 Reserve holders of Cobalt

1) DRC
2) Australia
3) Cuba


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