Thallium Atomic Number 81 Atomic Radius 156 pm
Protons 81 Block p
Neutrons 123 Group 13
Electrons 81 Period


Atomic Mass 204.38 Electron Configuration [Xe]4f145d106s26p1
Density 11.85g/cm3 Discovery 1861 in United Kingdom


Electrical Type Conductor
Melting Point 304°C Half-Life Stable
Boiling Point 1473°C Lifetime Stable

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Brief Description: When freshly exposed to air, Thallium exhibits a metallic luster, but soon develops a bluish-grey tinge, resembling Lead in appearance. A heavy oxide builds up on Thallium if left in air, and, in the presence of water, the hydroxide is formed. The metal is very soft and malleable. It can be cut with a knife. The element and its compounds are toxic and should be handled carefully. Thallium may cause cancer. There are no uses for metallic Thallium since pure Thallium quickly combines with oxygen and water vapor from the atmosphere, forming a black, powdery substance. Thallium, used in conjunction with Sulfur or Selenium and Arsenic, forms low melting glass.

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Last Updated: March 29, 2011