Copper

From PutterPedia

Copper is a reddish-colored metal, with a high electrical and thermal conductivity (silver is the only pure metal to have a higher electrical conductivity at room temperature).[1] In oxidation copper is mildly basic. Copper has its characteristic color because it reflects red and orange light and absorbs other frequencies in the visible spectrum, due to its band structure. This can be contrasted with the optical properties of silver, gold and aluminium. Copper occupies the same family of the periodic table as silver and gold, since they each have one s-orbital electron on top of a filled electron shell. This similarity in electron structure makes them similar in many characteristics. All have very high thermal and electrical conductivity, and all are malleable metals. In its liquified state, a pure copper surface without ambient light appears somewhat greenish, another characteristic shared with gold. Silver does not have this property, so it is not a complementary color for the orange incandescence color. When liquid copper is in bright ambient light, it retains some of its pinkish luster. Due to its high surface tension, the liquid metal does not wet surfaces but instead forms spherical droplets when poured on a surface. Copper is insoluble in water (H2O). There are two stable isotopes, 63Cu and 65Cu, along with a couple dozen radioisotopes. The vast majority of radioisotopes have half lives on the order of minutes or less; the longest lived, 67Cu, has a half life of 61.8 hours. See also isotopes of copper. Numerous copper alloys exist, many with important historical and contemporary uses. Speculum metal and bronze are alloys of copper and tin. Brass is an alloy of copper and zinc. Monel metal, also called cupronickel, is an alloy of copper and nickel. While the metal "bronze" usually refers to copper-tin alloys, it also is a generic term for any alloy of copper, such as aluminium bronze, silicon bronze, and manganese bronze. Copper is germicidal, via the oligodynamic effect. For example, brass doorknobs disinfect themselves of many bacteria within eight hours.[2] This effect is useful in many applications. The purity of copper is expressed as 4N for 99.99% pure or 7N for 99.99999% pure. The numeral gives the number of nines after the decimal point when expressed as a decimal (e.g. 4N means 0.9999, or 99.99%).