Hafnium: the essentials
Most zirconium minerals contain 1 to 3% hafnium. Hafnium is a ductile metal with a brilliant silver lustre. Its properties are influenced considerably by the impurities of zirconium present. Of all the elements, zirconium and hafnium are two of the most difficult to separate. Hafnium is a Group 4 transition element.
Because hafnium has a good absorption cross section for thermal neutrons (almost 600 times that of zirconium), has excellent mechanical properties, and is extremely corrosion resistant, it is used for nuclear reactor control rods.
Hafnium carbide is the most refractory binary composition known, and the nitride is the most refractory metal nitride (m.p. 3310°C).
Hafnium: historical information
Hafnium was thought to be present in various zirconium minerals many years prior to its discovery, in 1923, which was credited to Dirk Coster and George Charles von Hevesey. It was finally identified in zircon (a zirconium ore) from Norway, by means of X-ray spectroscopic analysis. It was named in honour of the city in which the discovery was made. A number of earlier claims seem less likely.
Most zirconium minerals contain 1 to 3% hafnium and it is their chemical similarity which made their separation difficult. It was originally separated from zirconium by repeated and tedious recrystallization of the double ammonium or potassium fluorides.
Hafnium around us Read more »
Hafnium has no biological role.
Hafnium is never found as the free element in nature. It is found in the ore alvite [(Hf, Th, Zr)SiO4.xH2O] and thortveitite. Most zirconium minerals (zircon, baddelyite) contain 1 to 3% hafnium and in practice most hafnium is produced as a byproduct of zirconium production, presumably because it is necessary to remove the hafnium from the zirconium used in the nuclear industries.
|Location||ppb by weight||ppb by atoms||Links|
|Human||(no data) ppb by weight||(no data) atoms relative to C = 1000000|
Physical properties Read more »
Heat properties Read more »
- Melting point: 2506 [2233 °C (4051 °F)] K
- Boiling point: 4876 [4603 °C (8317 °F)] K
- Enthalpy of fusion: 25.5 kJ mol-1
Crystal structure Read more »
The solid state structure of hafnium is: hcp (hexagonal close-packed).
Hafnium: orbital properties Read more »
Hafnium atoms have 72 electrons and the shell structure is 126.96.36.199.10.2. The ground state electronic configuration of neutral Hafnium is [Xe].4f14.5d2.6s2 and the term symbol of Hafnium is 3F2.
- Pauling electronegativity: 1.3 (Pauling units)
- First ionisation energy: 658.5 kJ mol‑1
- Second ionisation energy: 1440 kJ mol‑1
Isolation: hafnium extraction is always associated with its removal from zirconium as it is a contaminant of all zirconium minerals. Solvent extraction methods are used ot spearate the two metals but the process is not easy. These make use of the differential solubilities of the metal thiocyantes (thiocyanate is SCN-) in methyl isobutyl ketone.
Hafnium isotopes Read more »
Hafnium isotopes have several applications. Hf-180 is used for the production of the radioisotope Hf-181 while Hf-180 is used for the production of the radioisotope Ta-179, which has a medical application. The second isomer of Hf-178 (Hf-178m2) exhibits a very high excitation energy and it has been suggested for use in gamma ray lasers.
|174Hf||173.940044 (4)||0.16 (1)||0|
|176Hf||175.941406 (4)||5.26 (7)||0|
|177Hf||176.943217 (3)||18.60 (9)||7/2||0.7936|
|178Hf||177.943696 (3)||27.28 (7)||0|
|179Hf||178.9458122 (29)||13.62 (2)||9/2||-0.6409|
|180Hf||179.9465457 (30)||35.08 (16)||0|