Hafnium

Hafnium, symbol Hf, metallic element that closely resembles zirconium. Hafnium is one of the transition elements of the periodic table (see Periodic Law); the atomic number of hafnium is 72. Hafnium’s name comes from the Latin name for Copenhagen, Hafnia.

Hafnium was discovered in Copenhagen in 1923 by the Hungarian chemist Georg von Hevesy and the Dutch physicist Dirk Coster. On the basis of a prediction by the Danish physicist Niels Bohr that element 72 would resemble zirconium in structure, they looked for the element in zirconium ores. Hafnium is found in nearly all ores of zirconium. It resembles zirconium so closely in chemical properties and crystal structure that separation of the two elements is extremely difficult. Separation is accomplished most efficiently by means of the ion-exchange technique. Hafnium has been used in the manufacture of tungsten filaments. Because of its resistance to high temperatures, it is used with zirconium as a structural material in nuclear power plants. Hafnium compounds that function as semiconductors have been developed for use in computer chips.

Hafnium melts at about 2233°C (about 4051°F), boils at about 4603°C (about 8317°F), and has a specific gravity of 13.3. The atomic weight of hafnium is 178.49.