Hafnium

Source of the photo
http://periodictable.com/Elements/072/index.html
Author of the description
Gruiz Katalin

Atomic number

72

Atomic mass

178.49 g.mol -1

Electronegativity

1.3

Density

13.07 g.cm-3 at 20°C

Melting point

2200 °C

Boiling point

5200 °C

Vanderwaals radius

0.161 nm

Ionic radius

0.075 nm

Isotopes

10

Electronic shell

[ Xe ] 4f14 5d2 6s2

Energy of first ionisation

530 kJ.mol -1

Energy of second ionisation

1425.5 kJ.mol -1

Energy of third ionisation

2244.3 kJ.mol -1

Energy of fourth ionisation

3207.5 kJ.mol -1

Standard potential

- 1.68 V ( HfO2+/ Hf )

Discovered by

Dirk Coster in 1923

 

Hafnium is a lustrous, silvery, ductile metal. It restists corrosion due to formation of a tough, impenetrable oxide film on its surface. The metal is unaffected by alkalis and acids, except hydrofluoric acid. Hafnium is difficult to separate form its group 4 partner, zirconium, bacause the two elements have atoms that are the same size.

 

Applications

Hafnium and its alloys are used for control rods in nuclear reactors and nuclear submarines because hafnium is excellent at absorbing neutrons and it has a very high melting point and is corrosion resistant. It is used in high-temperature alloys and ceramics, since some of its compounds are very refractory: they will not melt except under the most extreme temperatures.