Hafnium

Symbol: Hf
Atomic number: 72
Category: transition metals
Group: 4
Period: 6
Block: d
Atomic weight: 17.849 g/mol
Electrons per shell: 2, 8, 18, 32, 10, 2
CAS number: 7440-58-6
Phase: solid
Density: 13.31 kg/l (near room temperature)
Melting point: 2506 K (2233C, 4051F)
Boiling point: 4876 K (4603C, 8317F)
Crystal structure: hexagonal
Oxidation states: 4
Electronegativity: 1.3 (Pauling scale)
Name's origin: Hafnia
Name's meaning: Copenhagen in Latin; the element was found in Copenhagen in 1923
Facts:
- is used in filaments, electrodes, and, more recently in integrated circuits
- is found combined in natural zirconium compounds but it does not exist as a free element in nature
- when divided into fine particles, it is pyrophoric and can ignite spontaneously in air