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 wasdiscovered by Dirk Coster and George Charles von Hevesy in 1923 at Denmark.Origin of name: from the Latin name "Hafnia" meaning "Copenhagen".
Isotope abundances of hafnium with the most intense signal set to 100%.
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.
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.
Density of solid: 13310 kg m-3
Molar volume: 13.44 cm3
Thermal conductivity: 23 W m‑1 K‑1
Melting point: 2506 [2233 °C (4051 °F)] K
Boiling point: 4876 [4603 °C (8317 °F)] K
Enthalpy of fusion: 20.5 kJ mol-1
Atomic radius (empirical): 155 pm
Molecular single bond covalent radius: 152 (coordination number 4) ppm
van der Waals radius: 253 ppm
Pauling electronegativity: 1.3 (Pauling units)
Allred Rochow electronegativity: 1.23 (Pauling units)
Mulliken-Jaffe electronegativity: (no data)
First ionisation energy: 658.52 kJ mol‑1
Second ionisation energy: 1410 kJ mol‑1
Third ionisation energy: 2176 kJ mol‑1
Universe: 0.7 ppb by weight
Crustal rocks: 3300 ppb by weight
Human: (no data) ppb by weight
