Chromium

Chromium is a bright, blue/white metal with excellent corrosion resistance. It is obtained by the aluminium reduction of Cr2O3, the source of which is chromite, a double oxide of chromium and iron which generally also contains magnesium. Chromium is soluble in HCl and H2SO4, but not in H3PO4, HNO3 or HClO4 due to the formation of a stable and insoluble oxide layer on its surface; this, along with its hardness, has been used to advantage in the chromium plating of steel which has good corrosion resistance. Chromium is alloyed with nickel in the manufacture of heat resisting alloys, and with iron, or nickel and iron, to produce stainless and heat resistant steels. Chromium is an important trace element for humans as it assists in the manufacture of glucose.


Symbol
Cr

Discovered
1780 by N.L. Vanquelin in Paris, France.

Abundance
100 ppm in the earth's crust.

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Atomic number 24 Clip
Atomic / Molecular Weight 51.996 gmol-1Clip
Density 7194 kgm-3Clip
Crystal Structure bcc Clip
Lattice constant 388 fmClip
Melting Point 2133 KClip
Boiling Point 2873 KClip
Linear expansivity 0.0000049 K-1Clip
Specific heat capacity 448 Jkg-1K-1Clip
Latent heat of fusion 134000 Jkg-1Clip
Thermal conductivity 96.5 Wm-1K-1Clip
Acoustic wave velocity (longitudinal bulk waves) 6608 ms-1Clip
Acoustic wave velocity (Irrotational waves) 6229 ms-1Clip
Acoustic wave velocity (Shear waves) 4005 ms-1Clip
Acoustic wave velocity (Rayleigh waves) 3655 ms-1Clip
Bulk Modulus of Rigidity 160100000000 Nm-2Clip
Electromotive Series 0.71 VClip
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See also: Chrome Plating, Chromium Dioxide, Chromium Oxide, Chromium VI Oxide, Periodic Table, Stainless Steel.

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Subjects: Chemistry