Bromine (Br)
Bromine is element 35, a halogen in period 4, group 17 of the periodic table. At room temperature it is a liquid.
Electron configuration [Ar] 3d10 4s2 4p5
Electrons per shell 2, 8, 18, 7
Bromine data
| Atomic number | 35 |
|---|---|
| Symbol | Br |
| Atomic mass | 79.904 u |
| Category | Halogen |
| Group | 17 |
| Period | 4 |
| Block | p |
| State at 25 °C | liquid |
| Melting point | 266 K (-7.1 °C) |
| Boiling point | 332 K (58.9 °C) |
| Density | 3.12 g/cm³ |
| Electronegativity (Pauling) | 2.96 |
| Atomic radius | 114 pm |
| 1st ionization energy | 1140 kJ/mol |
| Electron affinity | -325 kJ/mol |
| Oxidation states | -1, +1, +3, +4, +5, +7 |
| Common ion charge | − |
| Discovered | 1826 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through bromine’s configuration and its ions →
Where bromine sits
Bromine belongs to the halogens. Its Pauling electronegativity of 2.96 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Bromine FAQ
What is the electron configuration of bromine?
Bromine (Z = 35) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5. In noble-gas shorthand that is [Ar] 3d10 4s2 4p5.
How many valence electrons does bromine have?
7 (outer shell (n = 4)).
What is the atomic mass of bromine?
The standard atomic weight of bromine is 79.904 u, so one mole weighs 79.904 g.
Is bromine a metal?
No. Bromine is a halogen.
What is the charge of a bromine ion?
Bromine most commonly forms Br−.