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35Br79.904
Reactive Nonmetalsliquid at STPP-block

Bromine

Group: 17Period: 4Standard Atomic Weight: 79.904 u

Why is Bromine in this position?

Understanding the scientific rationale behind Bromine's position in the periodic table:

Group Assignment
Group 17

Belongs to Group 17 (Halogens) because it possesses 7 valence electrons (4s² 4p⁵).

Period Assignment
Period 4

Belongs to Period 4 because its outermost electrons occupy principal shell n=4.

Orbital Block
P-block

Belongs to the p-block because its differentiating electron enters a 4p orbital.

Chemical Category
Reactive Nonmetals

Classified as a reactive nonmetal due to its strong halogen electronegativity (2.96) and diatomic volatile liquid nature.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 7]

Bohr Atomic Shell Model(2, 8, 18, 7)

Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.

35 Protons (p⁺)45 Neutrons (n⁰)
KShell K: Electron 1 of 2Shell K: Electron 2 of 2LShell L: Electron 1 of 8Shell L: Electron 2 of 8Shell L: Electron 3 of 8Shell L: Electron 4 of 8Shell L: Electron 5 of 8Shell L: Electron 6 of 8Shell L: Electron 7 of 8Shell L: Electron 8 of 8MShell M: Electron 1 of 18Shell M: Electron 2 of 18Shell M: Electron 3 of 18Shell M: Electron 4 of 18Shell M: Electron 5 of 18Shell M: Electron 6 of 18Shell M: Electron 7 of 18Shell M: Electron 8 of 18Shell M: Electron 9 of 18Shell M: Electron 10 of 18Shell M: Electron 11 of 18Shell M: Electron 12 of 18Shell M: Electron 13 of 18Shell M: Electron 14 of 18Shell M: Electron 15 of 18Shell M: Electron 16 of 18Shell M: Electron 17 of 18Shell M: Electron 18 of 18NShell N: Electron 1 of 7Shell N: Electron 2 of 7Shell N: Electron 3 of 7Shell N: Electron 4 of 7Shell N: Electron 5 of 7Shell N: Electron 6 of 7Shell N: Electron 7 of 7BrZ = 35

Educational Note: This Niels Bohr planetary model visually illustrates principal quantum energy shells ($n=1, 2, 3\dots$) and electron counts. In modern quantum mechanics (Schrödinger model), electrons do not orbit in fixed circular planetary tracks, but exist as 3D probability clouds (orbitals: $s, p, d, f$) governed by the Heisenberg uncertainty principle.

Electron Shell Filling Breakdown

Shell K (n=1):2 / 2 electrons (100%)
Shell L (n=2):8 / 8 electrons (100%)
Shell M (n=3):18 / 18 electrons (100%)
Shell N (n=4):7 / 32 electrons (22%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵

Neutral ground state configuration. Valence electrons: 7.

Atomic & Quantum Properties

Electronegativity (Pauling)2.96 Pauling
1st Ionization Energy1139.9 kJ/mol
Electron Affinity-324.6 kJ/mol
Atomic Radius (empirical)94 pm
Common Oxidation States-1, +1, +3, +5
Crystal StructureOrthorhombic

Physical & Thermal Properties

Density at STP3.10 g/cm³
Melting Point-7.2 °C (265.95 K)
Boiling Point58.8 °C (331.95 K)
Magnetic OrderingDiamagnetic
Discovery Year1826
Discovered ByAntoine Jérôme Balard

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Brominated flame retardants (BFRs) in consumer electronics, plastics, and textiles
  • Traditional photographic film chemistry (Silver bromide / AgBr)
  • Clear brine completion fluids for high-pressure deep offshore oil drilling
  • Water treatment sanitizers for commercial hot tubs and swimming pools
Occurrence in Nature

Extracted from concentrated natural brines, ocean seawater, and salt lakes like the Dead Sea (which contains up to 5,000 ppm Br).

Etymology & Name Origin

From Greek 'bromos' meaning stench, due to its suffocating odor

Important Chemical Compounds
AgBr (Silver bromide)
HBr (Hydrobromic acid)
NaBr (Sodium bromide)
CH₃Br (Bromomethane)
Interesting Chemical Facts
  • Bromine and Mercury are the only two chemical elements in the entire periodic table that are liquids at standard room temperature and pressure (25 °C, 1 atm).
  • Bromine liquid readily evaporates at room temperature, giving off a dense, choking reddish-brown vapor that is three times denser than air.
  • The ancient royal purple dye (Tyrian purple) prized by Roman emperors was an organic dibromoindigo compound extracted from sea snails.
Safety & Handling Note

Liquid bromine causes severe, agonizing chemical burns that heal very slowly; inhaling the vapor causes fatal pulmonary edema.