Se
Selenium
Atomic number: 34Mass: 78.971 uCategory: Nonmetal
About Selenium
Selenium is a nonmetal with properties that are intermediate between those of its periodic table neighbours tellurium and sulfur. It is an essential trace element in the diet. Its electrical conductivity increases with light exposure, making it useful in photocopiers.
Properties
Period
4
Group
16
Block
P
Category
Nonmetal
Electronegativity
2.55 (Pauling)
Ionization Energy
941 kJ/mol
Melting Point
494 K (221°C)
Boiling Point
958 K (685°C)
Density
4.81 g/cm³
Oxidation States
-2, +2, +4, +6
Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴
[Ar] 3d¹⁰ 4s² 4p⁴
Shell 1:2e⁻
Shell 2:8e⁻
Shell 3:18e⁻
Shell 4:6e⁻
Real-World Uses
Photocopiers
Solar cells
Dietary supplements
Glass manufacturing
Pigments
Fun Fact
Selenium was named after the Moon (Selene in Greek) because it was always found alongside tellurium, which was named after the Earth.