Periodic Table > Bromine
 

Terminology


Allotropes
Some elements exist in several different structural forms, these are called allotropes.


For more information on Murray Robertson’s image see Uses and properties facts below.

 

Fact box terminology


Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.


Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.


Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp, principal, diffuse, and fundamental.


Atomic Number
The number of protons in the nucleus.


Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron Configuration
The arrangements of electrons above the last (closed shell) noble gas.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.


Melting Point (oC)
The temperature at which the solid-liquid phase change occurs.


Melting Point (K)
The temperature at which the solid-liquid phase change occurs.


Melting Point (oF)
The temperature at which the solid-liquid phase change occurs.


Boiling Point (oC)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (oF)
The temperature at which the liquid-gas phase change occurs.


Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.


Density (kgm-3)
Density is the weight of a substance that would fill 1 m3 (at 298 K unless otherwise stated).


Relative Atomic Mass
The mass of an atom relative to that of Carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists the value given is the abundance weighted average.


Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. 12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 neutrons).


CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact box

 
Group 17  Melting point -7.2 oC, 19.04 oF, 265.95 K 
Period Boiling point 58.8 oC, 137.84 oF, 331.95 K 
Block Density (kg m-3) 3120 
Atomic number 35  Relative atomic mass 79.904  
State at room temperature Liquid  Key isotopes 79Br 
Electron configuration [Ar] 3d104s24p5  CAS number 7726-95-6 
ChemSpider ID 4514586 ChemSpider is a free chemical structure database
 

Uses and properties terminology


Image Explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


Natural Abundance

Where this element is most commonly found in nature.


Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.


Appearance

The description of the element in its natural form.

Uses and properties

 
Image explanation
The image intends to reflect the rich colour, liquidity and aromatic nature of the element.
Appearance

Bromine is a deep-red, oily liquid with a sharp smell. It is toxic.

Uses

Bromine is used in many areas such as agricultural chemicals, dyestuffs, insecticides, pharmaceuticals and chemical intermediates. Some uses are being phased out for environmental reasons, but new uses continue to be found.

Bromine compounds can be used as flame retardants. They are added to furniture foam, plastic casings for electronics and textiles to make them less flammable. However, the use of bromine as a flame retardant has been phased out in the USA because of toxicity concerns.

Organobromides are used in halon fire extinguishers that are used to fight fires in places like museums, aeroplanes and tanks. Silver bromide is a chemical used in film photography.

Before leaded fuels were phased out, bromine was used to prepare 1,2-di-bromoethane, which was an anti-knock agent. 

Biological role

Bromine is present in small amounts, as bromide, in all living things. However, it has no known biological role in humans. Bromine has an irritating effect on the eyes and throat, and produces painful sores when in contact with the skin.

Natural abundance

Bromine is extracted by electrolysis from natural bromine-rich brine deposits in the USA, Israel and China. It was the first element to be extracted from seawater, but this is now only economically viable at the Dead Sea, Israel, which is particularly rich in bromide (up to 0.5%).

 
Atomic data terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron affinity (kJ mol-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *


Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, Ed in eV. χA - χB =(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2), with χH set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).


1st Ionisation energy (kJ mol-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).


Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic data

 
Atomic radius, non-bonded (Å) 1.850 Covalent radius (Å) 1.17
Electron affinity (kJ mol-1) 324.577 Electronegativity
(Pauling scale)
2.960
Ionisation energies
(kJ mol-1)
 
1st
1139.858
2nd
2083.213
3rd
3473.469
4th
4563.753
5th
5760.170
6th
8548.594
7th
9937.981
8th
18602.358
 
Bond enthalpies terminology

Covalent Bonds
The strengths of several common covalent bonds.

Bond enthalpies

 
Covalent bonds
Br–Br  192.9  kJ mol -1 C–Br  290  kJ mol -1 C–Br  285  kJ mol -1
Br–H  366.3  kJ mol -1  
 

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.


Key for numbers generated


Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9


Reserve base distribution

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)


Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %


Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)


Explanations for terminology


Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.


Sourced

The country with the largest reserve base.


Reserve Base Distribution

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.


Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.


Total Governance Factor

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.


Relative Supply Risk Index

The Crustal Abundance, Reserve Base Distribution, Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply risk

 
Scarcity factor 7.0
Country with largest reserve base USA
Crustal abundance (ppm) 0.88
Leading producer USA
Reserve base distribution (%) 63.60
Production concentration (%) 44.20
Total governance factor(production) 8
Top 3 countries (mined)
  • 1) USA
  • 2) China
  • 3) Spain
Top 3 countries (production)
  • 1) USA
  • 2) China
  • 3) Israel
 

Oxidation states and isotopes


Key for Isotopes


Half Life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Terminology


Common Oxidation states
The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.


Important Oxidation states
The most common oxidation states of an element in its compounds.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation states and isotopes

 
Common oxidation states 7, 5, 3, 1, -1
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  79Br 78.918 50.69
  81Br 80.916 49.31
 

Pressure and temperature - advanced terminology


Molar Heat Capacity (J mol-1 K-1)

Molar heat capacity is the energy required to heat a mole of a substance by 1 K.


Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, it provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.


Shear modulus (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.


Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.


Vapour Pressure (Pa)

Vapour pressure is the measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure and temperature data – advanced

 
Molar heat capacity
(J mol-1 K-1)
75.69 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) 1.9
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - - - - - - - - -
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History

Antoine-Jérôme Balard discovered bromine while investigating some salty water from Montpellier, France. He took the concentrated residue which remained after most of the brine had evaporated and passed chlorine gas into it. In so doing he liberated an orange-red liquid which he deduced was a new element. He sent an account of his findings to the French Academy’s journal in 1826.


A year earlier, a student at Heidelberg, Carl Löwig, had brought his professor a sample of bromine which he had produced from the waters of a natural spring near his home at Keruznach. He was asked to produce more of it, and while he was doing so Balard published his results and so became known at its discoverer.

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Podcasts

Listen to Bromine Podcast
Transcript :

Chemistry in its Element - Bromine


 

(Promo)

 

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.

 

(End promo)

 

Chris Smith

Hello, welcome to Chemistry in its Element where this week we're sniffing out the chemical that is named after the Greek word for stench and this substance has certainly kicked up a stink in its own right in its time because it makes holes in the ozone layer.   But it's not all bad as it's also given us drugs, insecticides and fire extinguishers and to tell the story of element number 35, here's chemist and author John Emsley.

 

John Emsley

Fifty years ago bromine was produced on a massive scale and turned into lots of useful compounds. Photography relied on the light-sensitivity of silver bromide, doctors prescribed potassium bromide as a tranquiliser, leaded petrol needed dibromomethane to ensure the lead was removed via the exhaust gases, bromomethane was widely used to fumigate soil and storage facilities, and fire extinguishers contained volatile organobromine compounds. Today these uses have all but disappeared.

World production of liquid bromine once exceeded 300,000 tonnes per year, of which a significant part was produced by a plant on the coast of Anglesey in Wales, which closed in 2004. This extracted the element from sea water, which contains 65 p.p.m. of bromide, and was done by using chlorine gas to convert the bromide to bromine which was then removed by blowing air through the water. 

The bromine story began with 24-year-old student Antoine-Jérôme Balard. He found that the salt residues left by evaporating brine from Montpellier, France, gave an oily red liquid when treated with acid. He realised this was a new element and reported it to the French Academy, who confirmed his discovery. When they realised it was chemically similar to chlorine and iodine they proposed the name bromine, based on the Greek word bromos  meaning stench.

While some uses of bromine have declined because the products made from it are no longer needed, others have been discouraged because of the damage this element could cause to the ozone layer. Volatile organobromine compounds are capable of surviving in the atmosphere long enough to reach the upper ozone layer where their bromine atoms are 50 times more damaging than the chlorine atoms - which are the main threat, coming as they did from the widely used chlorofluorocarbons, the CFCs. The Montreal Protocol which outlawed the CFCs sought also to ban the use of all volatile organobromines by 2010, and this restriction especially applied to the fumigant bromomethane and compounds such as CBrClF2 which were in fire extinguishers for electrical fires or those in confined spaces.

Bromomethane was a particular cause for concern but banning it has proved impossible because it has some uses for which alternatives have not been found. Often referred to as methyl bromide, CH3Br (boiling point 3.5oC), this has been widely employed to kill pests in the soil, in storage facilities, and to treat wood before it is exported. In the soil it kills nematodes, insects, bacteria, mites and fungi which threaten crops such as seed crops, lettuce, strawberries, grapes, and flowers such as carnations and chrysanthemums. 

In fact bromomethane is not quite so threatening as it first appears. Environmental research uncovered the unexpected result that half the bromomethane sprayed on soil never evaporates into the air because it is consumed by bacteria. Nor are man-made organobromines the main source of these compounds in the atmosphere. Marine plankton and algae release around half a million tonnes of various bromomethanes a year and in particularly tribromomethane (aka bromoform, CHBr3). 

Even more surprising has been the discovery that something in the oceans is making pentabromodiphenyl ether. This has been used as a fire-retardant, and when in 2005 it was found to be present in whale blubber it was at first thought to be the man-made variety. However, the carbon atoms it contained had detectable amounts of 14C meaning that they were of recent origin, whereas the fire retardant is made entirely from fossil resources and contains no 14C. Another complex bromine compound from the sea is the purple dye once used for clothes worn by the Roman Emperors. Tyrian purple as it was called was extracted from the Mediterranean mollusc Murex brandaris and this molecule contains two bromine atoms and is 6,6'-dibromoindigo.

Even when it appears benign as bromide ions in water, this element can still pose a threat to health. Ozonising drinking water in order to sterilise it converts any bromide to bromate (BrO3-) which is a suspected carcinogen and so must not exceed 10 p.p.b. And some reservoirs in California where this has been exceeded have had to be drained because of it.

Once so beneficial, bromine now appears to cause nothing but trouble. Yet in ways unseen, such as in the pharmaceutical industries, it still continues to be used to provide intermediates in the manufacture of live-saving drugs. 

 

 

Chris Smith

John Emsley unlocking the secrets of the brown element Bromine.   You can find out more about some of   John's other favourite elements in a series he has written for the RSC's Education in Chemistry and that's on line at rsc.org forward slash eduction.   Next time on Chemistry in its element Nobel prize winning chemist Kary Mullis explains why a soul of iron is essential.

 

Kary Mullis

For the human brain, iron is essential yet deadly. Carbon, sulfur, nitrogen. calcium, magnesium, sodium, maybe ten other elements are also involved in life, but none of them have the power of iron to move electrons around, and none of them have the power to totally destroy the whole system.   Iron does.  

 

Chris Smith

And you can catch Kary Mullis ironing out the wrinkles in metabolism's most important element on next week's Chemistry in its Element.   I'm Chris Smith, thank you for listening, see you next time.

 

(Promo)

 

Chemistry in its elementis brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements. 

 

(End promo)

 

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Resources

Description :
The Group 7 elements are called the halogens. This experiment involves some reactions of the halogens.
Description :
How does reactivity change upon descending the group?
Description :
Studying the physical characteristics of the group 7 non-metals known as the halogens
Description :
Each of the halogens forms a monovalent (singly-charged) anion. In this experiment you will be looking at the similarities and differences in some of the properties of these halide ions.
Description :
Demonstrating how the more reactive fluorine displaces the less reactive halogens
Description :
The halogens are elements of Group 7 of the Periodic table. This experiment illustrates some of the trends and similarities within the compounds of this group.
 

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References

 
Images:  Visual Elements © Murray Robertson 2011
Mining and Sourcing data:  British Geological Survey – natural environment research council.
Text:  John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.