Element: Thallium (Tl)

Element (Atom) NameThallium
Physical state at room temperatureSolid
Element ClassificationMetal
Group NameNone
Period Number (Periodic table) 6
Group number (Periodic table)13
Atomic number81
Atomic weight204.3833 (Ref: Jlab-ele081)
204.38 (Ref: Lanl-81)
[204.382, 204.385] (Ref: ciaaw-thallium, Nist-81)
Atomic Radius196 pm (Van der Waals) (Ref: Lanl-81)
Density11.8 g/cm3 (Ref: Jlab-ele081)
Melting point304°C (Ref: Jlab-ele081, Lanl-81)
Boiling point1473°C (Ref: Jlab-ele081, Lanl-81)
Electron shell configuration1s2 
2s2 2p6 
3s2 3p6 3d10 
4s2 4p6 4d10 4f14 
5s2 5p6 5d10
6s2 6p1
Oxidation States+3, +1 (Ref: Jlab-ele081)
3, 2, 1, −1, −2, −5 (Ref: Lanl-81)
Ionization Energy6.108 eV (Ref: Jlab-ele081)
6.1082873 eV (Ref: Nist-81)
Number of Stable Isotopes2
InChIInChI=1S/Tl (Ref: Pubchem-81)


  • Jlab-ele081: https://education.jlab.org/itselemental/ele081.html
  • Lanl-81: https://periodic.lanl.gov/81.shtml
  • ciaaw-thallium: https://www.ciaaw.org/thallium.htm
  • Nist-81: https://physics.nist.gov/cgi-bin/Elements/elInfo.pl?element=81
  • Pubchem-81: https://pubchem.ncbi.nlm.nih.gov/element/81
  • science.co.il: https://www.science.co.il/elements/

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