Bromine (symbol Br, atomic number 35) is one of only two elements liquid at room temperature, used in flame retardants. It is classified as a halogen and sits in group 17, period 4 of the periodic table.
Overview
Bromine is the chemical element with atomic number 35 and the symbol Br. With a standard atomic weight of 79.904, it is a halogen. In the periodic table it occupies group 17 and period 4, and under standard conditions it is normally a liquid. Bromine is one of only two elements liquid at room temperature, used in flame retardants.
Atomic structure
An atom of Bromine has 35 protons in its nucleus and, when neutral, 35 electrons arranged in the configuration [Ar] 3d10 4s2 4p5. Its standard atomic weight of 79.904 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Bromine was discovered in 1826 by Antoine Jérôme Balard. It follows Selenium (Se) and precedes Krypton (Kr) in order of atomic number.
| Atomic number | 35 |
|---|---|
| Symbol | Br |
| Atomic mass | 79.904 |
| Category | Halogen |
| Group | 17 |
| Period | 4 |
| Electron configuration | [Ar] 3d10 4s2 4p5 |
| Phase at STP | Liquid |
| Discovered | 1826 (Antoine Jérôme Balard) |