Chromium, chemical symbol Cr, elemental metal for the steel gray. Element's name comes from the Greek, meaning "color", because chromium compounds have colors. In 1797 the French chemist walker orchid (L.N.V auquelin) in the Siberian red lead chromium (lead) find a new mineral, the next year with carbon reduction. Chromium content in the earth's crust is 0.01%, the highest in 17th.
Nature does not exist the free state of chromium, chromium mainly exist in the lead. Ⅵ B clan in the periodic table of elements, chromium atomic number 24, atomic weight of 51.9961, body centered cubic crystal, common valency + 2, + 3 and + 6. Oxidation number is 6, 5, 4, 3, 2, 1, 1 -, 2 -, - 4, is one of the largest metal hardness.
Silvery white metal, quality is very hard, resistant to corrosion. The density of 7.20 g/cm3. Soluble in alkali solution. Chromium has the very high corrosion resistance, in the air, even in the red state, the oxidation is also slow. Does not dissolve in water. Plating on the metal can be protective.