---
title: "Bromine (Br): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/bromine.html
description: "Bromine (Br), element 35: atomic mass 79.904, electron configuration [Ar] 3d¹⁰ 4s² 4p⁵, group 17, period 4, p-block reactive nonmetal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
35Br79.904

# Bromine (Br) – element 35

Bromine is a chemical element with the symbol **Br** and atomic number **35**. It is a reactive nonmetal in group 17 (halogens), period 4 of the periodic table (p-block), and is a liquid at room temperature.

Bromine (Br) has atomic number 35, atomic mass 79.904 u and electron configuration [Ar] 3d10 4s2 4p5.

[Download periodic table PDF](https://www.moldraw.com/printables/periodic-table.pdf)[Open interactive periodic table](https://www.moldraw.com/tools/free-chem-tools/interactive-periodic-table.html)

## Bromine facts

| Symbol | Br |
| --- | --- |
| Atomic number | 35 |
| Atomic mass | 79.904 u (g/mol) |
| Category | reactive nonmetal |
| Group | group 17 (halogens) |
| Period | 4 |
| Block | p-block |
| Phase at 20 °C | Liquid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 |
| Noble-gas notation | [Ar] 3d10 4s2 4p5 |
| Electrons per shell | 2, 8, 18, 7 |
| Valence electrons | 7 |

## Bohr model and shells

Bromine has 35 electrons in 4 shells: 2, 8, 18, 7. Full configuration and noble-gas notation are in the table; work out any element or ion with the [electron configuration calculator](https://www.moldraw.com/tools/free-chem-tools/electron-configuration-calculator.html).

## Physical and atomic properties

| Melting point | 265.8 K (-7.3 °C) |
| --- | --- |
| Boiling point | 332 K (58.9 °C) |
| Density | 3.1028 g/cm³ |
| Electronegativity (Pauling) | 2.96 |
| Electron affinity | 324.537 kJ/mol |
| Ionization energies | 1139.9, 2103, 3470 kJ/mol (1st, 2nd, 3rd) |
| Discovered by | Antoine Jérôme Balard |

Use the atomic mass in the [molar mass calculator](https://www.moldraw.com/tools/free-chem-tools/molar-mass-calculator.html) for any formula containing Br.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of bromine?

The atomic mass of bromine is 79.904 u, so one mole of bromine atoms weighs 79.904 g.

### What is the electron configuration of bromine?

Bromine has 35 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵, or [Ar] 3d¹⁰ 4s² 4p⁵ in noble-gas notation. Electrons per shell: 2, 8, 18, 7.

### How many valence electrons does bromine have?

Bromine has 7 valence electrons (group 17).

### Is bromine a metal?

No. Bromine is a nonmetal (reactive nonmetal).

### Where is bromine on the periodic table?

Bromine is in group 17 (halogens), period 4, in the p-block.

Data: [Periodic-Table-JSON](https://github.com/Bowserinator/Periodic-Table-JSON) (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.