Atomic Element Z = 34 • Reactive Nonmetal
Selenium (Se) — Atomic Data, Electron Shells & Reactions
Selenium (symbol Se, atomic number 34) has a standard atomic weight of 78.971 u and ground-state configuration [Ar] 3d10 4s2 4p4.
Atomic Number (Z)
34
IUPAC Symbol
Se
Standard Atomic Weight
78.971 g/mol
Period / Group / Block
4 / 16 / p-block
Condensed Electron Config
[Ar] 3d10 4s2 4p4
Full Subshell Config
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4
Principal Shell Occupancy
[2, 8, 18, 6]
Pauling Electronegativity
2.55
First Ionization Energy
941 kJ/mol
Covalent Radius
120 pm
Melting Point
494 K (220.85 °C)
Boiling Point
958 K (684.85 °C)
Density
4.809 g/cm³
Oxidation States
+6, +4, -2
Se (Z=34) — Valence shell highlighted in vermilion