Element 35 · Halogen
Bromine (Br) — Element 35
Greek bromos — stench
Bromine (Br) is a halogen in Period 4, Group 17 of the periodic table with atomic number 35, standard atomic weight 79.904 u, and ground-state electron configuration [Ar] 3d¹⁰ 4s² 4p⁵. At standard temperature and pressure it is classified as a liquid with 7 valence electrons and common oxidation states -1, +1, +5.
Flame retardants, photography
What are the atomic properties and physical constants of Bromine?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 35
- Standard atomic mass
- 79.904 u
- Chemical family
- Halogen
- Ground-state configuration
- [Ar] 3d¹⁰ 4s² 4p⁵
- Electrons per shell
- 2, 8, 18, 7
- Valence electrons
- 7
- Common ion charges / oxidation states
- -1, +1, +5
- Phase at STP
- Liquid
- Pauling electronegativity
- 2.96 Pauling
- First ionization energy
- 1,140 kJ/mol
- Atomic radius
- 94 pm
- Melting point
- -7 °C
- Boiling point
- 59 °C
- Discovery year
- 1826
- Table coordinate
- Period 4, Group 17
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Bromine’s shells?
A neutral Bromine atom contains 35 electrons distributed across 4 occupied principal energy shells ([Ar] 3d¹⁰ 4s² 4p⁵). The table below compares Bromine’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Br | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 18 e⁻ | 18 e⁻ |
| n = 4 | N | 7 e⁻ | 32 e⁻ |
Frequently Asked Questions about Bromine (Br)
What is the atomic mass and atomic number of Bromine (Br)?
Bromine (Br) has atomic number Z = 35 (35 protons in its nucleus) and an IUPAC standard atomic weight of 79.904 u. It sits in Period 4, Group 17 and is classified as a halogen.
What is the ground-state electron configuration of Bromine?
The neutral ground-state electron configuration of Bromine (Z = 35) is [Ar] 3d¹⁰ 4s² 4p⁵. Across its 4 occupied principal shells (n = 1 to n = 4), the electrons per shell are 2, 8, 18, 7, with 7 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Bromine?
Bromine commonly forms -1, +1, +5 oxidation states or ion charges in compounds. Its Pauling electronegativity is 2.96 and its first ionization energy is 1,140 kJ/mol.
When was Bromine discovered and what is it used for?
Bromine was discovered in 1826 (Greek bromos — stench). Flame retardants, photography
How does Bromine compare to neighboring elements?
Other halogen elements: