The Element Hafnium
[Click for Isotope Data]
Atomic Number: 72
Atomic Weight: 178.49
Melting Point: 2506 K (2233°C or 4051°F)
Boiling Point: 4876 K (4603°C or 8317°F)
Density: 13.3 grams per cubic centimeter
Phase at Room Temperature: Solid
Element Classification: Metal
Period Number: 6 Group Number: 4 Group Name: none
What's in a name? From the Latin word for the city of Copenhagen, Hafnia.
Say what? Hafnium is pronounced as HAF-neeem.
History and Uses:
Hafnium was discovered by Dirk Coster, a Danish chemist, and Charles de Hevesy, a Hungarian chemist, in 1923. They used a method known as X-ray spectroscopy to study the arrangement of the outer electrons of atoms in samples of zirconium ore. The electron structure of hafnium had been predicted by Niels Bohr and Coster and Hevesy found a pattern that matched. Hafnium is difficult to separate from zirconium and is present in all of its ores. It is obtained with the same methods used to extract zirconium.
Hafnium is a good absorber of neutrons and is used in the control rods of nuclear reactors. Hafnium is also used in vacuum tubes as a getter, a material that combines with and removes trace gases from vacuum tubes. Hafnium has been used as an alloying agent in iron, titanium, niobium and other metals.
Melting near 3890°C, hafnium carbide (HfC) has the highest melting point of any known two-element compound. Hafnium nitride (HfN) also has a high melting point, around 3305°C. Other hafnium compounds include: hafnium chloride (HfCl4), hafnium fluoride (HfF4) and hafnium oxide (HfO2).
Estimated Crustal Abundance: 3.0 milligrams per kilogram
Estimated Oceanic Abundance: 7×10-6 milligrams per liter
Number of Stable Isotopes: 5 (View all isotope data)
Ionization Energy: 6.825 eV
Oxidation States: +4
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d2