conversion of one chemical element into another. A transmutation entails a change in the structure of atomic nuclei and hence may be induced by a nuclear reaction (q.v.), such as neutron capture, or occur spontaneously by radioactive decay, such as alpha decay and beta decay (qq.v.). Transmutation of base metals (such as mercury, tin, copper, lead) into precious metals (gold, silver) was long attempted by alchemists, who had no concept of the atomic nature of matter. Their experimentation led to discoveries of many important chemical reactions, but chemical reactions are not capable of effecting the nuclear changes required for transmutation.