Search this website:

This web page location:

home page  >   Chemical Elements  >   Thallium

Chemical Elements


Thallium sulfate, young shoot, Thallium, gamma radiation, infrared radiation

Deeper web pages:

>  Properties and Occurence

Thallium (Greek thallos, “young shoot”), symbol Tl, soft, malleable metallic element that acquires a bluish-gray color upon exposure to the atmosphere. Thallium is in group 13 (or IIIa) of the periodic table. The atomic number of thallium is 81.

Thallium was discovered spectroscopically in 1861 by the British chemist Sir William Crookes. It was isolated by Crookes and, independently, by the French chemist Claude August Lamy in 1862.


Thallium sulfate, which is odorless, tasteless, and very poisonous, is used to exterminate rodents and ants. Thallium-activated sodium iodide crystals mounted in photomultiplier tubes are used in some portable scintillation counters to detect gamma radiation. The abilities of thallium bromoiodide crystals to transmit infrared radiation and of thallium oxysulfide crystals to detect the same radiation have been employed extensively in military communication systems. Thallium alloyed with mercury forms a fluid metal that freezes at -60°C (-76°F); it is used in low-temperature thermometers, relays, and switches. Thallium salts, which burn with a bright green flame, are used in rockets and flares.

Article key phrases:

Thallium sulfate, young shoot, Thallium, gamma radiation, infrared radiation, periodic table, IIIa, ants, rodents, rockets, flares, relays, atmosphere, exposure, switches, Uses, group

Search this website: