A Visual Encyclopedia of the Periodic Table

120

Actinides

120

The most common natural radioactive metal,

thorium is used inside vacuum tubes to allow

an electric current to flow. It can also undergo

nuclear fission, a process in which atoms split in

two and release energy. Scientists are exploring

ways of making thorium-powered nuclear

reactors that produce electricity.

Neutron probe

Thorianite

This ore contains

uranium, which breaks

down into actinium.

This device

uses radioactive

actinium to

measure the

amount

of water.

Thorium

Rare in nature, actinium is a metal formed by

the decay of other radioactive elements. Its

atoms are unstable and break down to make the

elements francium and radon. Actinium is found

in tiny amounts in uranium ores, such as uranite,

and has limited applications. Its isotopes are

used in radiation therapy to treat cancer.

This radioactive

mineral glows brightly

in ultraviolet light.

Vacuum tube

This durable rock

made of solidified lava

contains 12% thorium.

This ore contains small

crystals of thorium compounds.

This thorium coating creates an

electric current by releasing electrons.

Actinium 89 89 138 State: SolidDiscovery: 1899

90 90 142

State: Solid

Discovery: 1829

Ac

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Th

90

A

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tu

ni

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U

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Mona

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120-121_Ac_Th_Pa.indd 120 02/12/16 10:05 pm