Bromine (Br)
[Ar] 3d¹⁰ 4s² 4p⁵. 1 unpaired electron, period 4, group 17, p block.
Element or ion
Type a symbol, a name or an atomic number, add a charge such as Fe3+ or Cl-, or tap an element in the table. Orbitals fill from m = −l up, spin +½ first.
BrBromine, Z = 35, 79.904 u
[Ar] 3d10 4s2 4p5
In full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵
- Blockp block
- Period4
- Group17
- Valence7
- Unpaired1
- MagneticPara
Last electron 4p
- n4shell
- l1p subshell
- m0orbital
- s−½spin down
Step by step
- Bromine has 35 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵.
- Write the subshells in order of n: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵.
- Replace the argon core with [Ar]: [Ar] 3d¹⁰ 4s² 4p⁵.
Bromine (Br): the numbers
| Atomic number | 35 |
|---|---|
| Atomic mass | 79.904 u |
| Period | 4 |
| Group | 17 |
| Block | p block |
| Valence electrons | 7 |
| Unpaired electrons | 1 |
| Magnetic | paramagnetic |
| Last electron | 4p: n = 4, l = 1, m = 0, s = −1/2 |
Bromine (Br): quick answers
What is the electronic configuration of bromine?
Bromine has 35 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵, or [Ar] 3d¹⁰ 4s² 4p⁵ in short.
How many unpaired electrons does bromine have?
Bromine has 1 unpaired electron, so it is paramagnetic. Put one electron in each box of a subshell before pairing (Hund’s rule) to see them.
What are the quantum numbers of the last electron of bromine?
The last electron goes into 4p: n = 4, l = 1, m = 0, s = −1/2. Orbitals fill from m = −l up, spin +½ first.