The Actinoid Series
Members of the Actinoid Series
The fifteen members of this series are actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium and lawrencium.
Properties
Actinoids share the following common properties:
All are radioactive.
All are highly electropositive.
The metals tarnish readily in air.
Actinoids are very dense metals with distinctive structures. Numerous allotropes may be formed (plutonium has at least 6 allotropes!).
They react with boiling water or dilute acid to release hydrogen gas.
Actinoids combine directly with most nonmetals.
Sources
Only actinium, thorium, and uranium occur naturally in the earth's crust in anything more than trace quantities. Neptunium and Plutonium have been known to show up naturally in trace amounts in uranium ores as a result of decay or bombardment. The remaining actinoids were discovered in nuclear fallout, or were synthesized in particle colliders. The latter half of the series possess exceedingly short half-lives.
Uses
Thorium is used in making strong alloys, ultraviolet photoelectric cells, mantles in portable gas lights and for coating tungsten wire.
Uranium is used as a fuel in nuclear reactors, depleted uranium is used in casings of armour piercing artillery shells, armour plating on tanks and as ballast in the wings of some large aircraft.
Neptunium is used in neutron detectors.
Plutonium is used in bombs and reactors.
Americium-241 is used in smoke detectors.
The other actinoids are too rare to be of any use.