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 | 1739 |
| Discovered by | Georg Brandt |
| Origin of the name | The name is derived from the German word 'kobald', meaning goblin. |
| 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 | 9 | Melting point | 1495°C, 2723°F, 1768 K |
| Period | 4 | Boiling point | 2927°C, 5301°F, 3200 K |
| Block | d | Density (g cm−3) | 8.86 |
| Atomic number | 27 | Relative atomic mass | 58.933 |
| State at 20°C | Solid | Key isotopes | 59Co |
| Electron configuration | [Ar] 3d74s2 | CAS number | 7440-48-4 |
| ChemSpider ID | 94547 | 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.
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.
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Specific heat capacity (J kg−1 K−1) |
421 | Young's modulus (GPa) | Unknown | |||||||||||
| Shear modulus (GPa) | Unknown | Bulk modulus (GPa) | Unknown | |||||||||||
| Vapour pressure | ||||||||||||||
| Temperature (K) |
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| Pressure (Pa) |
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Podcasts
Podcasts
| Listen to Cobalt Podcast |
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Transcript :
Chemistry in its element: cobalt (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 - beauty, blue glass, B12 and the best magnets that money can buy. So why is this week's element named after a goblin? Sarah Staniland I always find the question 'what's your favourite element' a difficult one. There are several front runners for vastly varying reasons; however, always a top contender has to be cobalt because it excels in several important character traits: Cobalt has amazing beauty and strength, as well as great cooperation. All together a highly useful metal. Before I even thought about the chemistry of colour I developed a love for blue glass, something I still collect to this day. Only after studying the transition metal chemistry did I realise that this beautiful blue colour comes from cobalt. Cobalt chloride in fact. However, as far as colours go, cobalt has a few more strings to its bow than just this wonderful blue. Cobalt can also colour glass green, while the hydrated form of cobalt chloride is a beautiful deep rose colour. As you can imagine this colour change due to the presence of water is highly useful, warranting cobalt chloride an ideal moisture indicator. The array of beautiful colours that cobalt produces were never more prevalent to me than when I went to the cobalt mining region called the Copperbelt in Zambia. In this area the huge multicoloured cobalt minerals deposits tower high, with the shores of dams and streams coloured deep rose with silvery blue veins running through. Cobalt it is not found pure in Nature but found in sulphur minerals and usually associated with other transition metals. As you can probably guess from the name of the region in Zambia - the Copperbelt, cobalt is mined as a secondary product to copper that is dominant in the ore of this region. Because of this cobalt is normally recovered from the waste of the primary metal extraction. However these mining hotspots are not the only places on the Earth where high concentrations of cobalt can be found. A huge reserve of several transition metals (including cobalt) can be found in strange nodules on the floors of the deepest oceans. The nodules are manganese minerals that take millions of years to form, and there are many tonnes of cobalt present in this form. So you can see that cobalt is never found alone but always palled up with other transition metals in their ores, mainly copper and nickel. In fact cobalt metal was not isolated and purified until as late as 1735 by the Swedish scientist G. Brandt. Cobalt can also sometimes be found in mixed arsenic ores, and it is cobalt's association with arsenic that gives it its name. The word cobalt comes from the German "Kobolds" which means goblin or trouble maker. It was so called in this early mining region because it was very difficult to smelt without oxidising and smelting would release the associated arsenic vapours which would lead to pretty troublesome or even deadly processing conditions for the worker. The Kobolds were blamed and the name stuck. With the exception of the mining region, cobalt is not very abundant, with only trace amounts in the Earths crust (about 2500 times less than iron). However, it is a metal that is essential for life in the trace amounts. Cobalt is the metal at the centre of vitamin B12 which helps regulate cell development and therefore DNA and energy production in the body. Cobalt has been known and used by people for its beautiful colouring and pigment properties as far back as 2500BC. Egyptian cobalt blue paints and Prussian cobalt oxide necklaces have been dated back to this time while cobalt glass has been found in a Greek vase dated at 100 BC. Cobalt was also used to colour glass in the Chinese Tang dynasty from 618 AD. In fact all the way up until the beginning of the 20th century people have only really exploited cobalt for its beautiful colour. However cobalt is not just a pretty face. Cobalt is a lustrous very hard silvery metal belonging to a group called the "transition metals". It is one of only 3 ferromagnetic transition elements along with iron and nickel. As a metal it is very mechanically hard and tough, and it has a very high melting point (hence the smelting problems) and also remains magnetic to the highest temperature of all the magnetic elements. When cobalt is combined with other metals its strength allow a range of super alloys to be created. In particular, cobalt's very high melting point and mechanical strength at high temperatures has seen its extensive use in what is termed 'superalloys'. These are alloys that retain mechanical strength at high temperatures. Because of its impressive properties cobalt is an important component in wear resistant and corrosive resistant alloys. And cobalt alloys and coatings are seen everywhere from drills to saws, from aircraft turbines to prosthetic bone replacements. The fact that cobalt is magnetic has also been exploited with the Japanese invention of cobalt magnetic steel where adding cobalt to steel vastly increases the magnetic hardness. Just a few years after that in the 1930s saw the pivotal invention of Alnico magnets, which as the name suggests, are composed of aluminium, nickel and cobalt. The fact that cobalt retains its magnetism up to high temperatures is also a very favourable trait when the addition of cobalt to a magnetic material can improve its properties at high temperatures. More recently the creation of rare-earth magnets have given us much stronger, harder, permanent magnets than Alnico magnets. One such magnetic material, samarium cobalt retains its magnetism up to 800°C. Because it is magnetically and mechanically hard up to very high temperatures, it has found uses in high-speed motors and turbo machinery. More recently cobalt has a major use in newer batteries, magnetic particles for recording and storage information in magnetic tapes and hard drives. So cobalt; giving joy in an array of beautiful colours, but also ultra strong, hard and magnetic. Cobalt is never alone, it is found associated with different metals in their ore and has its best mechanical properties when palled up with others. Chris Smith Emphasising the importance, of course, of teamwork. That was Sarah Staniland with the story of Cobalt - she's based at the University of Leeds. Next week it's the turn of the stuff that amongst other things makes Parker pen nibs write so nicely, but if you haven't heard of it before, then you're probably in good company. Jonathan Steed Stop the proverbial "man in the street" and ask him what ruthenium is and the chances are he won't be able to tell you. Compared to the "sexier elements" that are household names like carbon and oxygen, ruthenium is, frankly, a bit obscure. In fact even if your man in the street was wearing a lab coat and walking on a street very close to a university chemistry department he might still be a bit ignorant about this mysterious metal. It wasn't always that way, though. Chris Smith And you can hear how ruthenium rose to prominence with Jonathan Steed on next week's Chemistry in its Element. I'm Chris Smith, thank you for listening and goodbye. (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
Text © The Royal Society of Chemistry 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.
