Bromine (Br)
Bromine is the 35th element, a halogen in the p-block. Its standard atomic weight is 79.904.
Bromine
79.904
What the table records
- Atomic number
- 35
- Standard atomic weight
- 79.904
- Group
- 17
- Period
- 4
- Block
- p-block
- Category
- Halogen
- [Ar] 3d10 4s2 4p5
- Valence electrons
- 7
- Typical valence
- 1
- Van der Waals radius
- 1.9 Å
- Covalent radius
- 1.2 Å
Molecules containing bromine
The lightest named structures in this library that contain Br.
Bromide ion
Br- · 79.9 g/mol
Bromine atom
Br · 79.9 g/mol
Hydrogen Bromide
HBr · 80.91 g/mol
Methyl Bromide
CH₃Br · 94.94 g/mol
Hypobromite
BrO- · 95.9 g/mol
Hydrogen fluoride hydrogen bromide
H₂BrF · 100.92 g/mol
Cyanogen Bromide
CBrN · 105.92 g/mol
Bromoethene
C₂H₃Br · 106.95 g/mol
Ethyl Bromide
C₂H₅Br · 108.97 g/mol
Bromofluoromethane
CH₂BrF · 112.93 g/mol
BROMINE CHLORIDE (BrCl)
BrCl · 115.36 g/mol
Propargyl bromide
C₃H₃Br · 118.96 g/mol
How to read these numbers
The standard atomic weight is an average over the isotopes as they occur naturally, which is why it is rarely a whole number. It is the figure a molar mass calculation uses. Work in mass spectrometry wants the monoisotopic mass of a single isotope instead, which is a different number.
The two radii are not the same measurement. The covalent radius is half the distance between two bonded atoms of the element; the van der Waals radius is how close a non-bonded atom gets before repulsion takes over, and is always the larger. Space-filling models are drawn with the second, ball-and-stick models with the first — which is why the same molecule looks so different in the two.