34
Se
78.971
Selenium (Se)
Element 34 · Period 4 · Group 16
nonmetal
solid at room temp
p-block
About Selenium
Essential trace element. Used in glass-making, photocopiers, and solar cells.
Physical Properties
Atomic Mass
78.971 u
State at 25°C
Solid
Melting Point
220.8 °C
Boiling Point
685 °C
Density
4.809 g/cm³
Magnetism
Diamagnetic
Atomic Properties
Electron Configuration
[Ar] 3d¹⁰ 4s² 4p⁴
Electron Shells
2, 8, 18, 6
Electronegativity
2.55
Atomic Radius
103 pm
Ionization Energy
941 kJ/mol
Oxidation States
-2, +4, +6
Discovery & History
Discovered By
Jöns Jacob Berzelius
Discovery Year
1817
Named By
Jöns Jacob Berzelius
Name origin: Greek: Selene (Moon)
Frequently Asked Questions
- Is Selenium a metal, nonmetal, or metalloid?
- Selenium is classified as a nonmetal.
- What state is Selenium in at room temperature?
- Selenium is a solid at standard room temperature (25°C).
- What is the atomic mass of Selenium?
- Selenium has an atomic mass of 78.971 atomic mass units (u).
- Who discovered Selenium?
- Selenium was discovered by Jöns Jacob Berzelius in 1817.
- Where is Selenium on the periodic table?
- Selenium is element number 34, located in period 4 and group 16.