PERIODIC ELEMENT
Se (Selenium )

 



Atomic number : 34
Atomic mass : 79.96 g.mol-1
Electronegativity according to Pauling : 2.4
Density : 1.79 g.cm-3 at 20 °C
Melting point : 217 °C
Boiling point : 688 °C
Vanderwaals radius : 0.14 nm
Ionic radius : 0.198 nm (-2) ; 0.042 nm (+6)
Isotopes : 9
Electronic shell : [Ar] 3d10 4s24p4
Energy of first ionisation : 940.7 kJ.mol-1
Energy of second ionisation : 2045 kJ.mol-1
Energy of third ionisation : 2973.7 kJ.mol-1
Standard potential : - 0.77 V
Discovered by : Jons Berzelius 1817
 
Atomic Structure Uses (photoelectric cells, TV cameras)