WebElements

Periodic Table

hafnium

Atomic number: 72
Atomic weight: 178.49
Symbol: Hf
Group number: 4
Electronic configuration: [Xe].4f14.5d2.6s2

Description

Most zirconium minerals contain 1 to 5% 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 of all known metal nitrides (m.p. 3310°C).

General information

Discoveror: Dirk Coster and George Charles von Hevesy
Date discovered: 1923
Discovered at: Denmark
Meaning of name: From the Latin word "Hafnia" meaning "Copenhagen"

Physical data

Standard state: solid at 298 K
Colour: grey steel
Density of solid at ambient temperature/kg m-3: 13310
Molar volume/cm3: 13.44

Radii /pm

Atomic: 208
Covalent (single bond):
Pauling radius for the ion [Hf]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius177.9no data87.623.9

Electronegativities

Both values are quoted on the Pauling scale.

Pauling: 1.3
Allred Rochow: 1.23

Crystal Structure

structure: hcp (hexagonal close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.

ball-and-stick.gif

Temperatures (/K)

melting point: 2506
boiling point: 4876

Enthalpies /kJ mol-1

fusion: 25.0
vaporization: 626

single bond enthalpies:
Hf-F Hf-Cl Hf-Br Hf-I Hf-Hf
no data no data no data no data no data

Ionization enthalpies /kJ mol-1

Number Enthalpy
1st654
2nd1440
3rd2250
4th3210
5th6600

Isotopes

This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
174Hf173.940044 (4)0.162 (3)
176Hf175.941406 (4)5.206 (5)
177Hf176.943217 (3)18.606 (4)
178Hf177.943696 (3)27.297 (4)
179Hf178.9458122 (29)13.629 (6)
180Hf179.9465457 (30)35.100 (7)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Hf.html