Bromine (Br)
Element 35 · Halogen · Liquid at 25 °C · Group 17, Period 4
Bromine is one of only two elements that are liquid at room temperature — a dense, deep red-brown liquid whose compounds serve as flame retardants.
On the periodic table, bromine sits in group 17 — the halogens — in period 4. It is one of 6 elements classified as a halogen, and at room temperature (25 °C) it is a liquid — one of only 2 elements that are liquid under ordinary conditions.
The halogens of group 17 are one electron short of a full outer shell, which makes them ferociously good at grabbing electrons from other elements. Their name means “salt-former”: they combine with metals to make salts such as sodium chloride. They exist as diatomic molecules, and the group is the only one to span gas, liquid, and solid at room temperature. Reactivity decreases down the group.
Properties of bromine
| Atomic number (Z) | 35 |
|---|---|
| Symbol | Br |
| Atomic mass | 79.904 |
| Category | Halogen |
| Group | 17 |
| Period | 4 |
| Block | p-block |
| Metal / nonmetal | Nonmetal |
| State at 25 °C | Liquid |
| Electron configuration | [Ar] 3d10 4s2 4p5 |
| Electronegativity (Pauling) | 2.96 |
| Melting point | -7.2 °C (265.95 K / 19.04 °F) |
| Boiling point | 58.8 °C (331.95 K / 137.84 °F) |
| Density | 3.122 g/cm³ |
Position in the periodic table
Bromine shares group 17 — the halogens with Fluorine (F), Chlorine (Cl), Iodine (I), Astatine (At), Tennessine (Ts). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.
Within this dataset, it ranks #6 in electronegativity out of 99 elements with a pauling value.
Physical properties
Bromine melts at -7.2 °C (265.95 K / 19.04 °F) and boils at 58.8 °C (331.95 K / 137.84 °F), giving it a liquid range of about 66 °C at standard pressure.
Its density is 3.122 g/cm³.
See also: the interactive periodic table, how to read the periodic table, the element families tour.