Glossary
Allotropes
Some elements exist in several different structural forms, called allotropes. Each allotrope has different physical properties.
For more information on the Visual Elements image see the Uses and properties section below.
| Discovery date | 1826 |
| Discovered by | Antoine-Jérôme Balard in Montpellier, France and Carl Löwig in Heidelberg, Germany |
| Origin of the name | The name comes from the Greek 'bromos' meaning stench. |
| Allotropes |
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Glossary
Group
A vertical column in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.
Period
A horizontal row in the periodic table. The atomic number of each element increases by one, reading from left to right.
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 (s), principal (p), diffuse (d), and fundamental (f).
Atomic number
The number of protons in an atom.
Electron configuration
The arrangements of electrons above the last (closed shell) noble gas.
Melting point
The temperature at which the solid–liquid phase change occurs.
Boiling point
The temperature at which the liquid–gas phase change occurs.
Sublimation
The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.
Density (g cm−3)
Density is the mass of a substance that would fill 1 cm3 at room temperature.
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.
Isotopes
Atoms of the same element with different numbers of 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.
| Group | 17 | Melting point | −7.2°C, 19°F, 266 K |
| Period | 4 | Boiling point | 58.8°C, 137.8°F, 332 K |
| Block | p | Density (g cm−3) | 3.1028 |
| Atomic number | 35 | Relative atomic mass | 79.904 |
| State at 20°C | Liquid | Key isotopes | 79Br |
| Electron configuration | [Ar] 3d104s24p5 | CAS number | 7726-95-6 |
| ChemSpider ID | 4514586 | ChemSpider is a free chemical structure database | |
Glossary
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.
Appearance
The description of the element in its natural form.
Biological role
The role of the element in humans, animals and plants.
Natural abundance
Where the element is most commonly found in nature, and how it is sourced commercially.
History
History
Atomic radius, non-bonded
Half of the distance between two unbonded atoms of the same element when the electrostatic forces are balanced. These values were determined using several different methods.
Covalent radius
Half of the distance between two atoms within a single covalent bond. Values are given for typical oxidation number and coordination.
Electron affinity
The energy released when an electron is added to the neutral atom and a negative ion is formed.
Electronegativity (Pauling scale)
The tendency of an atom to attract electrons towards itself, expressed on a relative scale.
First ionisation energy
The minimum energy required to remove an electron from a neutral atom in its ground state.
Bond enthalpy (kJ mol−1)
A measure of how much energy is needed to break all of the bonds of the same type in one mole of gaseous molecules.
Glossary
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. Uncombined elements have an oxidation state of 0. The sum of the oxidation states within a compound or ion must equal the overall charge.
Isotopes
Atoms of the same element with different numbers of neutrons.
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 | |
Glossary
Data for this section been provided by the British Geological Survey.
Relative supply risk
An integrated supply risk index from 1 (very low risk) to 10 (very high risk). This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores.
Crustal abundance (ppm)
The number of atoms of the element per 1 million atoms of the Earth’s crust.
Recycling rate
The percentage of a commodity which is recycled. A higher recycling rate may reduce risk to supply.
Substitutability
The availability of suitable substitutes for a given commodity.
High = substitution not possible or very difficult.
Medium = substitution is possible but there may be an economic and/or performance impact
Low = substitution is possible with little or no economic and/or performance impact
Production concentration
The percentage of an element produced in the top producing country. The higher the value, the larger risk there is to supply.
Reserve distribution
The percentage of the world reserves located in the country with the largest reserves. The higher the value, the larger risk there is to supply.
Political stability of top producer
A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators.
Political stability of top reserve holder
A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators.
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Glossary
Specific heat capacity (J kg−1 K−1)
Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K.
Young's modulus
A measure of the stiffness of a substance. 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
A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain.
Bulk modulus
A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume.
Vapour pressure
A 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.
Podcasts
Podcasts
| Listen to Bromine Podcast |
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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 online at rsc.org/education. 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 element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements. (End promo)
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Video
Video
Resources
Resources
Terms & Conditions
Images © Murray Robertson 1999-2011
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© Murray Robertson 1998-2017.
Data
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
Uses and properties
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Supply risk data
Derived in part from material provided by the British Geological Survey © NERC.
History text
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Podcasts
Produced by The Naked Scientists.
Periodic Table of Videos
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
