Copper appears in the periodic table at the top of Group 11 above silver and gold. Collectively these are sometimes referred to as the coinage metals, although in modern times these metals are used less frequently than in the past.

Copper is one of the most important metals. Copper is reddish with a bright metallic lustre. It is malleable, ductile, and a good conductor of heat and electricity (second only to silver in electrical conductivity). Its alloys, brass and bronze, are very important. Monel and gun metals also contain copper. Apparently the reason that policemen in the USA are nicknamed "cops" or "coppers" is to do with their uniforms which used to have copper buttons.

Copper metal is not particularly reactive and indeed is found as the free metal ("native") on occasion. Copper sulfate is [Cu(SO 4 )(OH 2 ) 4 ].H 2 O in the crystalline state; it is particularly well known and was often called blue vitriol. The oxidation number in most copper compounds is Cu(II), old name cupric, but there are many important Cu(I) compounds (cuprous) as well.



Copper foil.

Copper (I) chloride salts imparts a blue colour to flames. The picture above shows the colour arising from adding cuprous chloride (CuCl) to a burning mixture of potassium chlorate and sucrose. This flame is relatively cool. Hotter flames burn green bacause of emission from copper atoms (only to be demonstrated by a professionally qualified chemist).