Nickel, 28 Ni General properties Pronunciation Template:Infobox element/pronunciation Appearance lustrous, metallic, and silver with a gold tinge Standard atomic weight (A r, standard ) Template:Infobox element/standard atomic weight Mass number Template:Infobox element/symbol-to-most-stable-isotope (most stable isotope)Nickel in the periodic table Template:Infobox element/periodic table Atomic number (Z ) 28 Group Template:Infobox element/group Period period 4 Block d-block Element category Template:Infobox element/category format Electron configuration [Ar ] 3d8 4s2 or [Ar] 3d9 4s1 Electrons per shell
2, 8, 16, 2 or 2, 8, 17, 1 Physical properties Phase at STP solid Melting point 1728 K (1455 °C, 2651 °F) Boiling point 3003 K (2730 °C, 4946 °F) Density (near r.t. ) 8.908 g/cm3 when liquid (at m.p. ) 7.81 g/cm3 Heat of fusion 17.48 kJ/mol [[Enthalpy of vaporization|Heat of Template:Engvar ]] 379 kJ/mol Molar heat capacity 26.07 J/(mol·K) [[Vapor pressure|Template:Engvar pressure ]] Atomic properties Oxidation states Template:Infobox element/symbol-to-oxidation-state Electronegativity Pauling scale: 1.91 [[Ionization energy|Template:Engvar energies]] 1st: 737.1 kJ/mol 2nd: 1753.0 kJ/mol 3rd: 3395 kJ/mol (more ) Atomic radius empirical: 124 pm Covalent radius 124±4 pm Van der Waals radius 163 pm Template:Infobox element/spectral lines Other properties Crystal structure Template:Infobox element/crystal structure Speed of sound thin rod 4900 m/s (at r.t. ) Thermal expansion 13.4 µm/(m·K) (at 25 °C) Thermal conductivity 90.9 W/(m·K) Electrical resistivity 69.3 nΩ·m (at 20 °C) Magnetic ordering ferromagnetic Young's modulus 200 GPa Shear modulus 76 GPa Bulk modulus 180 GPa Poisson ratio 0.31 Mohs hardness 4.0 Vickers hardness 638 MPa Brinell hardness 667–1600 MPa CAS Number 7440-02-0 History Discovery and first isolationAxel Fredrik Cronstedt (1751)Main isotopes of nickel Template:Infobox element/isotopes table | references
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↑ Carnes, Matthew; Buccella, Daniela; Chen, Judy Y.-C.; Ramirez, Arthur P.; Turro, Nicholas J.; Nuckolls, Colin; Steigerwald, Michael (2009). "A Stable Tetraalkyl Complex of Nickel(IV)". Angewandte Chemie International Edition . 48 (2): 3384. doi :10.1002/anie.200804435 . PMID 19021174 .
↑ Pfirrmann, Stefan; Limberg, Christian; Herwig, Christian; Stößer, Reinhard; Ziemer, Burkhard (2009). "A Dinuclear Nickel(I) Dinitrogen Complex and its Reduction in Single-Electron Steps". Angewandte Chemie International Edition . 48 (18): 3357. doi :10.1002/anie.200805862 . PMID 19322853 .