Iron - Fe, 26

The melting point of iron is 1535°C, boiling point is 2750°C, specific gravity is 7.874 (20°C), with a valence of 2, 3, 4, or 6. Pure iron is chemically reactive and corrodes rapidly, especially in moist air or at elevated temperatures. Four allotropic forms, or ferrites, are known: a, b, g, and d, with transition points at 770, 928, and 1530°C. The a form is magnetic, but when iron is transformed into the b form, the magnetism disappears, although the lattice remains unchanged.

Iron is vital to plant and animal life. In humans, it appears in the hemoglobin molecule. Iron metal is usually alloyed with other metals and carbon for commercial uses. Pig iron is an alloy containing about 3% carbon, with varying quantities of Si, S, P, and Mn. Pig iron is brittle, hard, and fairly fusible and is used to produce other iron alloys, including steel. Wrought iron contains only a few tenths of a percent of carbon and is malleable, tough, and less fusible than pig iron. Wrought iron typically has a fibrous structure. Carbon steel is an iron alloy with carbon and small amounts of S, Si, Mn, and P. Alloy steels are carbon steels that contain additives such as chromium, nickel, vanadium, etc. Iron is the least expensive, most abundant, and most used of all metals.