Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-gray, lustrous, hard and brittle transition metal. Chromium is the main additive in stainless steel, to which it adds anti-corrosive properties.
Chromium is found naturally in the Earths crust, in trace amounts. It can combined with other elements to form minerals such as chromite and the more rare crocoite. Chromium is mined as chromite ore, and is a common component of stainless steel. As an alloy, it can also be used in platings to improve surface hardness and corrosion resistance.
Chromium is a highly reactive element, and as such it is subject to oxidation and dissolution. In the presence of water or oxygen, chromium forms chromium oxide, which is very hard, brittle, and corrosion-resistant. This makes it ideal for use in the manufacture of stainless steel and other corrosion-resistant materials.
Chromium is also used in the production of dyes, for the tanning of leather goods, as a catalyst in chemical reactions, and as a catalyst for petroleum refining. It is used as a pigment in paints and plastics, and as a pigment for welding and glass-working applications. In addition, chromium is found in foods such as cereals, bread, and meats.
Chromium has the highest melting point of any metal and is the hardest of the transition elements, second only to tungsten in hardness. Its ductility makes it suitable for electroplating, while its corrosion resistance makes it valuable in chemical reaction vessels.
Chromium is also highly reactive chemically and has a tendency to oxidize and form compounds. The most commonly encountered oxidation state of chromium is +3, and is found in chromite ore, which is found refined as a compound in stainless steel. At higher temperatures, chromium will tend to form +6 oxidation states.
Chromium is also capable of forming hydrides, which are compounds consisting of hydrogen atoms bound to atoms of other elements. Chromium hydrides are relatively stable and can form complex molecules with up to four chromium atoms and four hydride atoms. These molecules have many industrial uses, notably in the making of high-performance materials such as stainless steel.
Chromium hydrides are also of importance in the making of hydrogen-bonded materials, such as polymers. The high reactivity of chromium hydrides makes them an appealing choice for creating new polymers and resins for use in the automotive and electronic industries.
Chromium has relatively low toxicity compared to the other transition elements, making it safe to use in industrial and domestic applications. It is however a known human carcinogen, and is thus only used in closed systems. Chromium salts are nonetheless used in the making of leather goods.
In conclusion, chromium is a versatile and invaluable element in the manufacture of corrosion-resistant materials, dyes, pigments, polymers, and other industrial products. It is relatively non-toxic and is relatively inert, making it safe to use in many applications.
