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Promethium - Pm

Chemical properties of promethium - Health effects of promethium - Environmental effects of promethium

Atomic number


Atomic mass

(147) g.mol -1

Electronegativity according to Pauling



6.475 g.cm-3 at 20°C

Melting point

1168 °C

Boiling point

2460 °C

Vanderwaals radius


Ionic radius




Electronic shell

[ Xe ] 4f5 6s2

Energy of first ionisation

534.6 kJ.mol -1

Energy of second ionisation

1050 kJ.mol -1

Standard potential

- 2.42 V

Discovered by

Marinsky 1945

Promethium - Pm


Promethium is a rare-earth metal that emits beta radius. It is very radoiactive and rare, so it is little studied: its chemical and physical properties are not well defined. Promethium salts have a pink or red colour that coluors the surroundings air with a pale blue-green light.


Most promethium is used for research purpose. It can be used as beta radiation source in luminous paint, in nuclear batteries for guided missiles, watches, pacemakers and rados, and as a light source for signals. It is possible that in future it will be used as portable X-ray source.

Promethium in the environment

Promethium dose occurs in the Earth's crust in tiny amounts in some uranium ores. It is not stable so it undergoes radioactive decay. All the promethium which might once have existed on Earth when it formed would have vanished within 10000 years.

Health effects of promethium

Promethium has no role to play on living things and is slightly dangerous because of its intense radioactivity. Test on animals showed that it become localized on the surface of bones from which it can be only slowly removed.

Environmental effects of promethium

Promethium is practically non-existent in nature, so it poses no threat to the environment. It has to be haldled carefully because of its high radioactivity.

Back to chart periodic elements.

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