The Golden Excess

It has been demonstrated that nuclear properties such as spin, parity and stability are functions of more than atomic number, characterizing these as properties of nuclides rather than elements. Other properties, usually thought of as functions of atomic number only, may well be of the same type. One such property is superconductivity, first observed as a property of certain metals at low temperature. Periodic variation of superconductivity with atomic number has been analyzed by many authors [103, 105, 106]. A number of trends appear to be well established. Pure elemental superconductivity is restricted to metals, but many semi-metals and non-metals become superconducting under special conditions such as cooling at high pressure or after structural modification. Whereas the critical temperature for non-metals increases with applied pressure, the inverse is often observed for superconducting metals. Superconductivity cannot be induced in ferromagnetic or anti-ferromagnetic metals.