Atomic number:24

Group numbers:6

Period:4

Electronic configuration:[Ar] 3d⁵ 4s¹

Formal oxidation number:+2 +3 +6

Electronegativities:1.66

Atomic radius / pm:124.9

Relative atomic mass:51.9961 ± 0.0006

 

Chromium was discovered by Louis-Nicholas Vauquelin (FR) in 1797. The origin of the name comes from the Greek word chroma meaning colour. It is a very hard, crystalline, steel-grey metal. The pure metal has a blue-white colour. It is hard, brittle and corrosion-resistant at normal temperatures. Hexavalent compounds are toxic by skin contact. The most important chromium mineral is chromite [Fe,Mg(CrO4)]. It is produced commercially by heating its ore in the presence of silicon or aluminium. Chromium is used to make stainless steel; it gives the colour to rubies and emeralds. Iron-nickel-chromium alloys in various percentages yield an incredible variety of the most important metals in modern technology.

Density / g dm^-3:7190 (293 K)

 6460 (m.p.)

Molar volume / cm³mol^-1:7.23 (293 K)

 8.05 (m.p.)

Electrical resistivity / μΩcm:12.9 (20 °C)

Thermal conductivity / W m^-1K^-1:93.7

Melting point / °C:1907

Boiling point / °C:2671

Heat of fusion / kJ mol^-1:15.3

Heat of vaporization / kJ mol^-1:341.8

Heat of atomization / kJ mol^-1:394.51

1st ionization energy / kJ mol^-1:652.87

2nd ionization energy / kJ mol^-1:1590.64

3rd ionization energy / kJ mol^-1:2987.21

in the atmosphere / ppm:-

in the Earth's crust / ppm:185

in the oceans / ppm:0.00005