- a gray, toxic metallic element with a high melting point (over 2000°C), found in most zirconium minerals. Symbol: Hf; atomic weight: 178.49; atomic number: 72; specific gravity: 12.1.
- a bright metallic element found in zirconium ores: used in tungsten filaments and as a neutron absorber in nuclear reactors. Symbol: Hf; atomic no: 72; atomic wt: 178.49; valency: 4; relative density: 13.31; melting pt: 2231±20°C; boiling pt: 4603°C
rare element, 1923, Modern Latin, from Hafnia, Medieval Latin form of Danish Havn “harbor,” the usual pre-1400 name of Copenhagen, Denmark, where it was discovered by physicist Dirk Coster (1889-1950) and chemist George de Hevesy (1885-1966).
n. Symbol Hf
- A metallic element found with zirconium and used in nuclear reactor control rods and in tungsten alloys used in filaments. Atomic number 72.
- A bright, silvery metallic element that occurs in zirconium ores. Because hafnium absorbs neutrons better than any other metal and is resistant to corrosion, it is used to control nuclear reactions. Atomic number 72; atomic weight 178.49; melting point 2,220°C; boiling point 5,400°C; specific gravity 13.3; valence 4. See Periodic Table.