34Se
Selenium
Reactive NonmetalSelenium (Se) is element 34, a reactive nonmetal, in period 4 and group 16 of the periodic table. Its standard atomic weight is 78.971, it melts at 221 °C and boils at 685 °C. Discovered by Jons Jacob Berzelius, 1817.
Atomic Number34
SymbolSe
NameSelenium
Atomic Weight78.971 u
CategoryReactive Nonmetal
Period4
Group16
Melting Point221 °C
Boiling Point685 °C
Density4.809 g/cm³
Electron Config[Ar] 3d10 4s2 4p4
Discovered ByJons Jacob Berzelius, 1817