Bromine

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Other names/abbreviations:

Br

Element no:	35
Element group:	17 (IUPAC) VII A (American labelling) VII B (European labelling) Halogens
Element type:	Nonmetals
CAS-Number:	7726-95-6
EINECS-Number:	231-778-1

Chemical properties

Reaction of bromine with metals/metal ions
Cd reacts directly with Br₂ in aqueous solution and Br₂ (g) at 450 °C [5].

Cd (s) + Br₂ (aq) Cd²⁺ (aq) + 2 Br^- (aq)
Cd (s) + Br₂ (g) CdBr₂ (s) [pale yellow]


Mn(II)-ions are readily oxidized to MnO₂ by brome under alkaline conditions

Mn²⁺ (aq) + Br₂ (aq) + 2 OH^- (aq) MnO₂ (s) [brown-black] + 2 HBr (aq)

Manganese with oxidation steps >2 will be reduced to Mn(II) by Br^- under acidic conditions under the formation of Br₂, e.g.

MnO₂ (s) + 2 Br^- (aq) + 4 H⁺ (aq) Mn²⁺ (aq) + Br₂ (aq) + 2 H₂O (l)


Nickel(II) can be oxidized to nickel(III) using Br₂ under alkaline conditions

2 Ni(OH)₂ (s) + Br₂ (aq) + 2 OH^- (aq) 2 Ni(OH)₃ (s) + 2 Br^- (aq)


Solubility
Water: 42 g/L (0 °C) [2]

Safety

Symbol: T+, C
R-phrases: 26-35
S-phrases: 7/9-26-45

Physical properties

Appearance
	Physical state @ 20°C:	Liquid [1]
	Color:	Solid: Pale yellow [1] Liquid: Red-brown [1]
	Odor:	Biting [2]

Bulk properties
	Molecular weight (g/mol):	79.904(1) [1]
	Melting point (°C):	-7.2 [2]
	Boiling point (°C):	58.8 (1013 mbar) [2]
	Ignition temperature (°C):	Not flammable [2]
	Flash point (°C):	Not combustible [2]
	Density (g/cm3):	3.12 (20 °C) [2]
	Relative vapour density (g/cm3):	5.5 (20 °C) [2]

Optical properties
	Refractive index:	1.661 [3]

Thermodynamic properties
	ΔfH°gas (kJ/mol):	111.9 (monoatomic) [3] 30.9 (Br2) [3]
	ΔfH°liquid (kJ/mol):	0.0 [3]
	ΔH°fusion (kJ/mol):	10.57 (Br2) [3]
	S°gas (J/K·mol):	175.0 (monoatomic) [3] 245.5 (Br2) [3]
	S°liquid (J/K·mol):	152.2 (Br2) [3]
	ΔfG°gas (kJ/mol):	82.4 (monoatomic) [3] 3.1 (Br2) [3]
	Cp (gas) (J/K·mol):	20.8 (monoatomic, 25 °C) [3] 36.0 (Br2, 25 °C) [3]
	Cp (liquid) (J/K·mol):	75.7 (Br2, 25 °C) [3]
	Cp (solid) (J/K·mol):	36.057 (Br2, 25 °C) [3]
	Critical temperature (°C):	315 [3]

Electronic properties
	Electron configuration:	1s2-2s2-2p6-3s2-3p6-3d10-4s2-4p5
	Ionic radius (Å):	Br(-I) 1.96 (coordination number 6) [2]
	Electron affinity [M-M-] (kJ/mol):	324.5 [1]

Misc.
	Vapour pressure (Pa):	22000 (20 °C) [2]

History

Discovery
Discovered by Antoine-Jérôme Balard in 1826. Bromine was not prepared in quantity until 1860 [3].

Origin of name
From Greek "bromos" meaning stench [3].

References

1: Greenwood,N.N., Earnshaw,A. Chemistry of the elements
2nd edition (1997) Edited by Greenwood,N.N., Earnshaw,A. pp. 1-1340, Butterworth-Heinemann. Oxford. Great Britain

2: Merck. ChemDAT The Merck Chemical Database Ver. 1.1.5

3: CRC Handbook of Chemistry and Physics
75th edition (1994) Edited by Lide,D.R. , CRC Press Inc. Boca Raton, USA

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© Michael Pilgaard
Created: April 29, 2006
Last update: October 10, 2008