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    204.3833 (2)

    Name: thalliumGroup number: 13
    Symbol: TlGroup name: (none)
    Atomic number: 81Period number: 6
    Atomic weight: 204.3833 (2)Block: p-block
    CAS Registry ID: 7440-28-0Voice:
    Standard state: solid at 298 KColour: silvery white
    Classification: MetallicAvailability:


    When freshly exposed to air, thallium exhibits a metallic lustre, 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.

    Nearing Zero cartoon for thallium
    Nearing Zero cartoon included by kind permission of Nick Kim.


    Here is a brief summary of the isolation of thallium.

    Thallium metal would not normally be made in the laboratory as it is available commercially. Crude thallium is present as a component in flue dust along with arsenic, cadmium, indium, germanium, lead, nickel, selenium, tellurium, and zinc. This is done by dissolving in dilute acid, precipitating out lead sulphate, and then adding HCl to precipitate thallium chloride, TlCl. Further purification can be achieve by electrolysis of soluble thallium salts.

  • TlF
  • TlF3
  • Chlorides
  • TlCl
  • TlCl2
  • TlCl3
  • Bromides
  • TlBr
  • Tl2Br4
  • Iodides
  • TlI
  • TlI3
  • Hydrides
    none listed
  • Tl2O
  • Tl2O3
  • Sulfides
  • Tl2S
  • Selenides
  • Tl2Se
  • Tellurides
    none listed
    none listed

    Our data and resources are taken from Web Elements