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Osmium

Source of the photo
http://periodictable.com/Elements/076/index.html
Author of the description
Gruiz Katalin

Atomic number

76

Atomic mass

190.2 g.mol -1

Electronegativity

2.2

Density

22.5 g.cm-3 at 20°C

Melting point

3045 °C

Boiling point

5027 °C

Vanderwaals radius

0.136 nm

Ionic radius

0.067 nm (+4)

Isotopes

13

Electronic shell

[ Xe ] 4f14 5d- 6s2

Energy of first ionisation

838 kJ.mol -1

Standard potential

+ 0.85 V (Os2+/ Os )

Discovered by

Smithson Tennant in 1803

 

Osmium is lustrous, silvery metal, one of the so-called platinum group of metals. It is the densest metal known, althoung only by the narrowest margins. Osmium is uneffected by water and acids, but dissolves with molten alkalis. Osmium powder reacts slowly with the oxygen of the air and gives off detacteble amounts of osmium tetroxide vapour.

Applications

The metal is used in a few alloys and in industry as a catalyst. At one time it was to be encountered in the nibs of high-quality fountain pens, compass needles, long-life gramophone needles and clock bearings, thanks to its extreme hardness and corrosion resistance.