Selenium

Koushik 26/06/2026 19:58:08 Updated 26/06/2026 19:58:08

Property	Value
Atomic Number	34
Element	Selenium
Symbol	Se
Atomic Mass	78.971 u
Number of Neutrons	46 (most common isotope, Selenium-80)
Number of Protons	34
Number of Electrons	34
Period	4
Group	16
Phase	Solid
Radioactive	No
Natural	Yes
Metal	No
Nonmetal	Yes
Metalloid	No
Type	Polyatomic Nonmetal
Atomic Radius	103 pm
Electronegativity	2.55 (Pauling scale)
First Ionization Energy	9.752 eV
Density	4.81 g/cm³
Melting Point	221 °C
Boiling Point	685 °C
Number of Isotopes	6 stable (Se-74, Se-76, Se-77, Se-78, Se-80, Se-82)
Discoverer	Jöns Jacob Berzelius
Year	1817
Specific Heat	0.321 J/g·K
Number of Shells	4
Number of Valence Electrons	6