Chemical element with atomic number 27 (Co)
Cobalt, 27 Co Pronunciation [ 1] Appearance hard lustrous bluish gray metal
Atomic number (Z ) 27 Group group 9 Period period 4 Block d-block Electron configuration [Ar ] 3d7 4s2 Electrons per shell 2, 8, 15, 2 Phase at STP solid Melting point 1768 K (1495 °C, 2723 °F) Boiling point 3200 K (2927 °C, 5301 °F) Density (at 20° C) 8.834 g/cm3 [ 4] when liquid (at m.p. ) 7.75 g/cm3 Heat of fusion 16.06 kJ/mol Heat of vaporization 377 kJ/mol Molar heat capacity 24.81 J/(mol·K) Vapor pressure
P (Pa)
1
10
100
1 k
10 k
100 k
at T (K)
1790
1960
2165
2423
2755
3198
Oxidation states −3, −1, 0, +1, +2 , +3 , +4, +5[ 5] (an amphoteric oxide) Electronegativity Pauling scale: 1.88 Ionization energies 1st: 760.4 kJ/mol 2nd: 1648 kJ/mol 3rd: 3232 kJ/mol (more ) Atomic radius empirical: 125 pm Covalent radius Low spin: 126±3 pm High spin: 150±7 pm Spectral lines of cobaltNatural occurrence primordial Crystal structure hexagonal close-packed (hcp) (hP2 ) Lattice constants a = 250.71 pmc = 407.00 pm (at 20 °C)[ 4] Thermal expansion 12.9× 10−6 /K (at 20 °C)[ a] 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 Speed of sound thin rod 4720 m/s (at 20 °C) Poisson ratio 0.31 Mohs hardness 5.0 Vickers hardness 1043 MPa Brinell hardness 470–3000 MPa CAS Number 7440-48-4 Discovery and first isolationGeorg Brandt (1735)
Category: Cobalt | references
child table, as reused in {IB-Co}
^ "cobalt". Oxford English Dictionary (2nd ed.). Oxford University Press . 1989.
^ "Standard Atomic Weights: Cobalt" . CIAAW . 2017.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)" . Pure and Applied Chemistry . doi :10.1515/pac-2019-0603 . ISSN 1365-3075 .
^ a b Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements . Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9 .
^ Greenwood, Norman N. ; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann . pp. 1117–1119. ISBN 978-0-08-037941-8 .
^ a b Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF) . Chinese Physics C . 45 (3): 030001. doi :10.1088/1674-1137/abddae .
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