Periodic Table
34
Se
78.971
Selenium
NonmetalPhotoconductive; used in photocells & xerography.
Electronic Configuration
[Ar] 3d¹⁰ 4s² 4p⁴or1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴
Electron shells
2e⁻n=1
8e⁻n=2
18e⁻n=3
6e⁻n=4
Properties
Atomic number
34
Atomic mass
78.971 u
Category
Nonmetal
Block / Group / Period
p · 16 · 4
Valence electrons
6
Oxidation states
-2, +4, +6
Electronegativity
2.55
Atomic radius
103 pm
Ionization energy
941 kJ/mol
Electron affinity
195 kJ/mol
Melting point
494 K / 221 °C
Boiling point
958 K / 685 °C
Density
4.809 g/cm³
State at 25 °C
solid
Personal Notes
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