Lenntech Water treatment & purification Lenntech Water treatment & purification

Neptunium - Np

Chemical properties of neptunium - Healt effects of neptunium - Environmental effects of neptunium

Atomic number


Atomic mass

(237) g.mol -1

Electronegativity according to Pauling



20.25 g.cm-3 at 20°C

Melting point

640 °C

Boiling point

3902 °C

Vanderwaals radius


Ionic radius




Discovered by

McMillan in 1940

Neptunium - Np


Neptunium is a ductile, silvery, radioactive metal. Neptunium forms numerous chemical compounds. Chemically it is extremely reactive and is attacked by oxygen, steam and acids, but not by alkalis. It can exist in many oxidation states, from neptunium (II) to neptunium (VII).


Neptunium has been used in neutron detectors. It does not have any commercial application.

Neptunium in the environment

Neptunium occurs naturally in Earth, being present in minute quantities in uranium ores. Today neptunium-237 is extracted in kg quantities from the spent uranium fuel rods of nuclear reactors.

Health effects of neptunium

Neptunium plays no rule in living things an is never encountered outside nuclear facilities or research laboratories.

Possible health effects: Bone cancer

Organ receiving main dose: Gastrointestinal tract

Summary of health studies: Most of the neptunium that is retained in the body deposits in the bones. Some is also retained in the liver. Several studies report "relatively high concentrations" of neptunium in adrenal glands of laboratory animals.

No health effects specific to exposure from neptunium "have been observed" in human beings. Roy C. Thompson, Biology Department of Battelle Pacific Northwest Laboratory in Richland, conducted an extensive review of studies involving neptunium. This review included Russian studies that found an increase in the number of bone tumors in animals receiving bone doses as low as a few rad. Thompson concluded that "there can be little doubt" that neptunium can cause cancer in bone.

In 1984, a team of German scientists reported preliminary results of an experiment with mice designed to measure the combined effect of having neptunium-239 deposit in bone and decay into plutonium-239. These initial results found evidence that the buildup of plutonium-239 (as the neptunium decayed) increased the number of bone tumors compared to those expected from exposure to neptunium alone.

Environmental effects of neptunium

No negative environmental effects have been reported. If you have any information on these, please contact us and tell us.

Back to chart periodic elements.

About Lenntech

Lenntech BV
Distributieweg 3
2645 EG Delfgauw

tel: +31 152 610 900
fax: +31 152 616 289
e-mail: info@lenntech.com

Copyright © 1998-2018 Lenntech B.V. All rights reserved