Periodic Table of the Elements
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Bottom FACULTY OF CHEMICAL TECHNOLOGY o PERIODIC TABLE OF THE ELEMENTS Bottom
  A B C D E F G H I J K L M N O P R S T U V X Z  
Periodic Table of the Elements Tableau périodique des éléments Periodni sustav elemenata Tavola periodica degli elementi Das Periodensystem der Elemente
Cobalt Cobalt Kobalt Cobalto Kobalt

 
Atomic number: 27
Group numbers: 9
Period: 4
 
Discovery date: 1735
Co

Cobaltum
NEIGHBOURS

 
 
 
26
Fe
 27
Co
 28
Ni
44
Ru
 45
Rh
 46
Pd


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Cobalt was discovered by Georg Brandt (Germany) in 1735. The origin of the name comes from the German word kobald meaning goblin or evil spirit. It is hard, ductile, lustrous bluish-grey metal. Surfaces stable in air. Reacts over time with dilute acids. It has remarkable magnetic properties.
Bottom TRANSITION ELEMENT: COBALT GROUP Top

Relative atomic mass: 58.933200(9) Electronic configuration: [Ar] 3d7 4s2
Formal oxidation number: +2 +3 Electronegativities: 1.88
Thermal conductivity: 100 W m-1 K-1 Electrical resistivity (20 °C): 6.24 μΩcm
Atomic radius: 125.3 pm Standard state (20 °C): solid
Density (g dm-3): 8900 (293 K)
7670 (m.p.)		 Molar volume (cm3 mol-1): 6.62 (293 K)
7.68 (m.p.)


Bottom THERMAL PROPERTIES Top

Melting point: 1495 °C Heat of fusion: 15.2 kJ mol-1
Boiling point: 2927 °C Heat of vaporization: 382.4 kJ mol-1
Critical temperature: 5127 °C Heat of atomization: 423.082 kJ mol-1


Bottom IONIZATION ENERGIES AND ABUNDANCE Top

1st ionization energy: 760.41 kJ mol-1 Abundance of element (air): - ppm
2nd ionization energy: 1648.27 kJ mol-1 Abundance of element (Earth's crust): 29 ppm
3rd ionization energy: 3232.28 kJ mol-1 Abundance of element (oceans): 0.0005 ppm


Bottom ISOTOPES Top

Isotopes Relative atomic mass Abundance (%)
59Co58.933200(2)100


Bottom MINERALS AND USES Top

Cobalt occurs in compounds with arsenic and sulfur as in cobaltine (CoAsS) and linneite (Co3S4). Pure cobalt is obtained as a by-product of refining nickel, copper and iron. Used in many hard alloys; for magnets, ceramics and special glasses. Radioactive cobalt-60 is used in cancer therapy. The price of 99.9 % pure cobalt pieces is 171.20 € for 500 g.

Bottom REDUCTION POTENTIALS Top

Balanced half-reaction   Eo / V      Annotation
Co3+ + e- = Co2+ +1.808  
Co2+ + 2e- = Co(s) - 0.277  
Co3O4(s) + 8H+ + 2e- = 3Co2+ + 4H2O +2.11  
Co2O3(s) + 6H+ + 2e- = 2Co2+ + 3H2O +1.75  
Co(OH)2(s) + 2e- = Co(s) + 2OH- - 0.73  
Co(NH3)63+ + e- = Co(NH3)62+ +0.1  
CoO(OH)(s) + H2O + e- = Co(OH)2(s) + OH- +0.17  

 

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