Chemical element
Selenium
- Se
- Z = 34
- nonmetal
Selenium (Se) is element 34, a nonmetal in period 4 and group 16. Its standard atomic weight is 78.971 Da. Weights follow IUPAC standard atomic weights, 2021 revision.
Identity
SymbolSe
Standard atomic weight78.971atomic mass units (Da)
Mass in kilograms1.3113443 × 10^-25
Categorynonmetal
Group16
Period4
Blockp-block
Electrons in a neutral atom34
Neutrons in the most common isotope45≈
Quantities
Molar mass78.971 g/mol
Mass of one mole78.971 grams
Atoms in one gram7.6257623 × 10^21
Mass of one atom1.3113443 × 10^-22 g
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