Recognised as Chemical element
Bromine
- Br
- Z = 35
- halogen
Bromine (Br) is element 35, a halogen in period 4 and group 17. Its standard atomic weight is 79.904 Da. Weights follow IUPAC standard atomic weights, 2021 revision.
Identity
SymbolBr
Standard atomic weight79.904atomic mass units (Da)
Mass in kilograms1.3268371 × 10^-25
Categoryhalogen
Group17
Period4
Blockp-block
Electrons in a neutral atom35
Neutrons in the most common isotope45≈
Electron configuration
Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵ground state, subshells written in order of n
Noble gas shorthand[Ar] 3d¹⁰ 4s² 4p⁵
Electrons per shell2, 8, 18, 7K, L, M and outward
Electrons in the outer shell7
Unpaired electrons1Hund's rule; unpaired electrons make the free atom paramagnetic
Madelung ruleFollowedthe ground state is what the n + l filling order predicts
Quantities
Molar mass79.904 g/mol
Mass of one mole79.904 grams
Atoms in one gram7.53672 × 10^21
Mass of one atom1.3268371 × 10^-22 g
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