Chromium

cromo

Chromium is named after chroma, the Greek word meaning "color". Many chromium minerals, including chromite and chrocoite, are brightly colored. An artificial form of crocoite, known as "chromium yellow", was used in paints, but was banned due to the toxicity of chromium salts. Pure chromium does not corrode easily, so it is combined with carbon oxide and carbon to produce stainless steel. Chromium also gives gemstones, such as rubies, their deep red color. Chrome-plated bodywork and parts are also used in vehicles, giving them a shiny finish.

Summary of properties (Cr)

Atomic weight51.9961(6)
Discoverer (year)Vauquelin (1797)
Natural formmetallic solid (body centered cubic)
Electron configuration[Ar] 3d5 4s1
Melting point (ºC)1857
Boiling point (ºC)2672
Abundance in earth's crust (ppm)102
Isotope (abundance)50Cr (4.345), 52Cr (83.789), 53Cr (9.501), 54Cr (2.365)
Density g/cm37.19
Van der Waals radius (pm)206
Covalent radius (pm)130
Electronegativity (Pauling)1.55
Vaporization enthalpy (kJ/mol)348.80
Enthalpy of fusion (kJ/mol)21.00
Specific heat capacity (J/g·K) at 25ºC and 1 atm0.45
Thermal conductivity (W/cm·K) at 25ºC and 1 atm0.940
Oxidation state+6, +3, +2
Electron affinity (eV)0.67
1st Ionization potential (eV)6.7665

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