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27
Co
58.93
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Cobalt. Photo by Ben Mills
| Classification: | Cobalt is a transition metal |
| Color: | bluish-white |
| Atomic weight: | 58.9332 |
| State: | solid |
| Melting point: | 1495 oC, 1768 K |
| Boiling point: | 2930 oC, 3203 K |
| Shells: | 2,8,15,2 |
| Electron configuration: | [Ar] 3d7 4s2 |
| Density @ 20oC: | 8.90 g/cm3 |
| Atomic volume: | 6.7 cm3/mol |
| Structure: | hcp: hexagonal close pkd |
| Hardness: | 5.0 mohs |
Discovery of Cobalt
Since ancient times cobalt compounds have been used to produce blue glass and ceramics.
The element was first isolated by George Brandt in 1735. He showed it was the presence of the element cobalt that caused the blue color in glass, not bismuth as previously thought.
In about 1741 he wrote, "As there are six kinds of metals, so I have also shown with reliable experiments... that there are also six kinds of half-metals: a new half-metal, namely cobalt regulus in addition to mercury, bismuth, zinc, and the reguluses of antimony and arsenic."
The word cobalt is derived from the German 'kobold', meaning goblin or elf.
Appearance & Characteristics
Adding HCl shifts the equilibrium and color of a cobalt chloride solution.
HCl added to the pink colored Co2+ solution results in the formation of a blue colored solution of CoCl42- ions.
The reaction is reversible and the colors can switch back and forth when the Cl- concentration changes.
Harmful effects:
Cobalt and its compounds are considered to be slightly toxic by skin contact and moderately toxic by ingestion.
Characteristics:
Cobalt is a bluish-white, lustrous, hard, brittle metal. It is ferromagnetic.
The metal is active chemically, forming many compounds.
Cobalt stays magnetic to the highest temperature of all the magnetic elements (it has a Curie point of 1121oC).
Cobalt is used in alloys for aircraft engine parts and in alloys with corrosion/wear resistant uses.
Cobalt is widely used in batteries and in electroplating.
Cobalt salts are used to impart blue and green colors in glass and ceramics.
Radioactive 60Co is used in the treatment of cancer.
Cobalt is essential to many living creatures and is a component of vitamin B12.
Cobalt is also used in samarium-cobalt permanent magnets. These are used in guitar pickups and high speed motors.
Cobalt and its compounds are considered to be slightly toxic by skin contact and moderately toxic by ingestion.
Characteristics:
Cobalt is a bluish-white, lustrous, hard, brittle metal. It is ferromagnetic.
The metal is active chemically, forming many compounds.
Cobalt stays magnetic to the highest temperature of all the magnetic elements (it has a Curie point of 1121oC).
Uses of Cobalt
Cobalt is used in alloys for aircraft engine parts and in alloys with corrosion/wear resistant uses.
Cobalt is widely used in batteries and in electroplating.
Cobalt salts are used to impart blue and green colors in glass and ceramics.
Radioactive 60Co is used in the treatment of cancer.
Cobalt is essential to many living creatures and is a component of vitamin B12.
Cobalt is also used in samarium-cobalt permanent magnets. These are used in guitar pickups and high speed motors.
Abundance & Isotopes
Abundance earth's crust: 25 parts per million by weight, 8 parts per million by moles
Abundance solar system: 4 parts per million by weight, 0.7 parts per million by moles
Cost, pure: $21 per 100g
Cost, bulk: $4.40 per 100g
Source: Cobalt is not found as a free element in nature. It is found in mineral ores. The main ores of cobalt are cobaltite (CoAsS), erythrite (hydrated arsenate of cobalt), glaucodot (Co,Fe)AsS, and skutterudite (Co,Ni)As3.
Cobalt is generally produced as a by-product of nickel and copper mining.
Isotopes: Cobalt has 22 isotopes whose half-lives are known, with mass numbers 50 to 72. Of these, only one is stable, 59Co.
Abundance solar system: 4 parts per million by weight, 0.7 parts per million by moles
Cost, pure: $21 per 100g
Cost, bulk: $4.40 per 100g
Source: Cobalt is not found as a free element in nature. It is found in mineral ores. The main ores of cobalt are cobaltite (CoAsS), erythrite (hydrated arsenate of cobalt), glaucodot (Co,Fe)AsS, and skutterudite (Co,Ni)As3.
Cobalt is generally produced as a by-product of nickel and copper mining.
Isotopes: Cobalt has 22 isotopes whose half-lives are known, with mass numbers 50 to 72. Of these, only one is stable, 59Co.
Energies
Specific heat capacity: 0.42 J g-1 K-1
Heat of fusion: 16.190 kJ mol-1
1st ionization energy: 758.4 kJ mol-1
3rd ionization energy: 3232.2 kJ mol-1
Heat of fusion: 16.190 kJ mol-1
1st ionization energy: 758.4 kJ mol-1
3rd ionization energy: 3232.2 kJ mol-1
Heat of atomization: 426 kJ mol-1
Heat of vaporization: 373.3 kJ mol-1
2nd ionization energy: 1646 kJ mol-1
Electron affinity: 63.8 kJ mol-1
Heat of vaporization: 373.3 kJ mol-1
2nd ionization energy: 1646 kJ mol-1
Electron affinity: 63.8 kJ mol-1
Oxidation & Electrons
Shells: 2,8,15,2
Minimum oxidation number: -1
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 1.88
Minimum oxidation number: -1
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 1.88
Electron configuration: [Ar] 3d7 4s2
Maximum oxidation number: 5
Max. common oxidation no.: 3
Polarizability volume: 7.5 Å3
Maximum oxidation number: 5
Max. common oxidation no.: 3
Polarizability volume: 7.5 Å3
Reactions & Compounds
Reaction with air: mild, w/ht ⇒ Co3O4
Reaction with 15 M HNO3: vigorous, ⇒ Co(No3)2, Nox
Oxide(s): CoO, Co3O4
Hydride(s): None
Reaction with 15 M HNO3: vigorous, ⇒ Co(No3)2, Nox
Oxide(s): CoO, Co3O4
Hydride(s): None
Reaction with 6 M HCl: mild, ⇒ H2, CoCl2
Reaction with 6 M NaOH:
Chloride(s): CoCl2
Reaction with 6 M NaOH:
Chloride(s): CoCl2
Radius
Atomic radius: 135 pm
Ionic radius (2+ ion): 83.8 pm
Ionic radius (2- ion): pm
Ionic radius (2+ ion): 83.8 pm
Ionic radius (2- ion): pm
Ionic radius (1+ ion): pm
Ionic radius (3+ ion): 71.8 pm
Ionic radius (1- ion): pm
Ionic radius (3+ ion): 71.8 pm
Ionic radius (1- ion): pm
Conductivity
Thermal conductivity: 100 W m-1 K-1
Electrical conductivity: 17.9 x 106 S m-1
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