Chromium, is a steel gray metal. There is no free chromium in nature, which mainly exists in chromium-lead ore. The atomic number of chromium is 24, atomic weight is 51.9961, and body-centered cubic crystal is the hardest metal.
Chromium is a silver-white lustrous metal. Pure chromium is ductile. Chromium containing impurities is hard and brittle. The density was 7.20g/cm3. It is soluble in strong alkali solution. Chromium has a high corrosion resistance and oxidation is slow in the air, even in the state of red heat. It is insoluble in water. Plating on metals can provide protection.
Chromium can dissolve slowly in dilute hydrochloric acid and sulfuric acid to form blue solution. Contact with air turns green because it is oxidized to green CrCl3. However, chromium is insoluble in concentrated nitric acid and is passive due to the formation of a compact oxide film on the surface. Chromium can be directly combined with halogen, sulfur, nitrogen and carbon at high temperature.
Chromium is used to make stainless steel, automotive parts, tools, tapes and videos. Chromium plating on metal can prevent rust, also known as Keduomi, strong and beautiful.