Cr is the symbol of metal chromium, and the symbol of chromium element is Cr, a silvery white metal, belonging to VI B group in the periodic table of elements. The atomic number of chromium is 24, the atomic weight is 5 1.996 1, and the common valences of body-centered cubic crystals are +3, +6 and +2. The oxidation value is 10. 1797, French chemist L.N.Vauquelin discovered a new element in Siberian galena, which was reduced by carbon the following year to obtain metallic chromium. Because chromium can produce beautiful and colorful compounds, it is named chromium according to the color of the Greek word.

Chromium is an important alloying element. Chromium is added to steel and alloy in the form of metallic chromium and ferrochrome.

Silvery white metal, extremely hard and corrosion resistant. The density is 7.20g/cm3. Soluble in strong alkali solution. Chromium has high corrosion resistance and is slowly oxidized in air, even in red heat. Insoluble in water. Electroplating on metal can play a protective role.