Copper

Copper is the metallic chemical element of atomic number 29, symbol Cu, atomic weight 63.55, specific gravity 8.96, melting point 1,985°F (1,085°C), and boiling point 4,645.4°F (2,563°C). It consists of two stable isotopes, of mass numbers 63 (69.1%) and 65 (30.9%).

Copper is one of only two metals that are colored, Copper is reddish brown, while gold is...gold—a unique color that is sometimes loosely described as yellow. All other metals are silvery, with various degrees of brightness or grayness. Almost everybody handles copper just about every day in the form of pennies. But because a piece of copper the size of a penny has become more valuable than one cent, today's pennies are made of zinc, with just a thin coating of copper.

Copper is in group 11 of the periodic table, along with silver and gold. This trio of metals is sometimes referred to as the coinage metals, because they are relatively valuable, corrosion-free and pretty, which makes them excellent for making coins. Strangely enough, the penny is the only American coin that is not made from a copper alloy. Nickels, dimes, quarters, and half dollars are all made from alloys of copper with other metals. In the case of nickels, the main metal is of course nickel.

Copper is one of the elements that are essential to life in tiny amounts, although larger amounts can be toxic. About 0.0004% of the weight of the human body is copper. It can be found in such foods as liver, shellfish, nuts, raisins and dried beans. Instead of the red hemoglobin in human blood, which has an iron atom in its molecule, lobsters and other large crustaceans have blue blood containing hemocyanin, which is similar to hemoglobin but contains a copper atom instead of iron.