Symbol: Tl

Periodic Table Information

Thallium on the periodic table is located in between Mercury and Lead and directly below Indium. It is a part of the aluminum family, and is in period 6 and group 13 (IIIA) in the transition metals. Its atomic number is 81and has an atomic mass of 204.4 (rounded to the nearest tenth). It has 81 protons and electrons, and 123 neutrons.

Occurrences in Nature, Uses, and Characteristics

Thallium is uncommon in nature, but can be found in the minerals crookesite, lorandite, and hutchinsonite. It is used in rat poison, infrared radiation detection, and photocells. Thallium is a very soft and malleable metal with a melting point of 303.5 degrees Celsius. When freshly exposed to air, thallium has a silvery-white luster, but soon develops a bluish tinge.

Discovery and Interesting(?) Facts

  • Thallium was discovered by Sir William Crookes in 1861 in England.
  • Thallium's name comes from Greek word "thallos"
  • Thallium is very toxic and use of it is limited in the U.S.
  • You can buy it on Amazon for 40$ a pound.


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