Element: Selenium (Se)

Element (Atom) NameSelenium
Physical state at room temperatureSolid
Element Classificationnon-metal
Group NameChalcogen
Period Number (Periodic table) 4
Group number (Periodic table)16
Atomic number34
Atomic weight78.971 (Ref: Jlab-ele034, ciaaw-selenium, Nist-34)
78.96 (Ref: Lanl-34)
Atomic Radius190 pm (Van der Waals) (Ref: Lanl-34)
Density4.809 g/ml (Ref: Jlab-ele034)
Melting point220.5°C (Ref: Jlab-ele034)
221 °C (Ref: Lanl-34)
Boiling point685°C (Ref: Jlab-ele034, Lanl-34)
Electron shell configuration1s2 
2s2 2p6 
3s2 3p6 3d10 
4s2 4p4
Oxidation States+6, +4, -2 (Ref: Jlab-ele034)
6, 5, 4, 3, 2, 1, −1, −2 ​(a strongly acidic oxide) (Ref: Lanl-34)
Ionization Energy9.752 eV (Ref: Jlab-ele034)
9.752392  eV (Ref: Nist-34)
Number of Stable Isotopes6
InChIInChI=1S/Se (Ref: Pubchem-34)


  • Jlab-ele034: https://education.jlab.org/itselemental/ele034.html
  • Lanl-34: https://periodic.lanl.gov/34.shtml
  • ciaaw-selenium: https://www.ciaaw.org/selenium.htm
  • Nist-34 : https://physics.nist.gov/cgi-bin/Elements/elInfo.pl?element=34
  • Pubchem-34: https://pubchem.ncbi.nlm.nih.gov/element/34
  • science.co.il: https://www.science.co.il/elements/

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