It is toxic and was used in rat poison. Bismuth has a low melting point. Automatic fire sprinklers have a plug of bismuth which melts when it gets too hot. Polonium is used in special anti-static brushes. Radon is a gas used in radiation therapy for cancer.
Radium is used in luminous paint.
Actinium is used as a source of neutrons. Thorium is used in the glowing mantles in gas lanterns. Protactinium is very rare and has few uses. It is used in nuclear power plants and nuclear weapons. Neptunium is used in neutron detectors.