The physical properties of metals are directly related to the number of delocalized electrons they have. In general, the more delocalized electrons a metal has, the better its electrical and thermal conductivity, as well as its malleability and ductility. For example, copper, which has one delocalized electron per atom, is an excellent conductor of electricity and heat, and is also very malleable and ductile. On the other hand, tungsten, which has six delocalized electrons per atom, is a poor conductor of electricity and heat, and is also very hard and brittle.