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 | 1817 |
| Discovered by | Friedrich Stromeyer |
| Origin of the name | The name is derived from the Latin 'cadmia', the name for the mineral calamine. |
| Allotropes | - |
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 | 12 | Melting point | 321.069°C, 609.924°F, 594.219 K |
| Period | 5 | Boiling point | 767°C, 1413°F, 1040 K |
| Block | d | Density (g cm−3) | 8.69 |
| Atomic number | 48 | Relative atomic mass | 112.414 |
| State at 20°C | Solid | Key isotopes | 114Cd |
| Electron configuration | [Kr] 4d105s2 | CAS number | 7440-43-9 |
| ChemSpider ID | 22410 | 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 | |
| Common oxidation states | 2 | ||||
| Isotopes | Isotope | Atomic mass | Natural abundance (%) | Half life | Mode of decay |
| 106Cd | 105.906 | 1.25 | > 1.9 x 1019 y | EC, EC | |
| 108Cd | 107.904 | 0.89 | > 4.1 x 1017 y | EC EC | |
| 110Cd | 109.903 | 12.49 | - | - | |
| 111Cd | 110.904 | 12.8 | - | - | |
| 112Cd | 111.903 | 24.13 | - | - | |
| 113Cd | 112.904 | 12.22 | 8.04 x 1015 y | β-β- | |
| 114Cd | 113.903 | 28.73 | > 1.3 x 1018 y | β-β- | |
| 116Cd | 115.905 | 7.49 | 3.8 x 1019 y | β-β- | |
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 Cadmium Podcast |
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Transcript :
Chemistry in its element: cadmium (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, this week we're learning a very painful lesson about a heavy metal Steve Mylon Ouch Ouch ! I cannot imagine that this is all someone would be saying if they were unfortunate enough to be stricken with the disease of the same name. That's right, the ouch-ouch disease. From the description, it seems like the pain would be intense enough to make me say a lot more than just ouch-ouch. Itai-Itai is the original Japanese for ouch ouch. The disease results from excessive cadmium poisoning and was first reported in a small town about 200 miles north west of Tokyo. There, rice grown in cadmium contaminated soils had more than 10 times the cadmium content than normal rice. Excess cadmium began to interfere with calcium deposition in bones. The ouch-ouch-ness of this disease resulted from weak and brittle bones subject to collapse due to high porosity. It is amazing to think that cadmium was able to accumulate to such high levels that it could overwhelm the human body's already intense defenses against it. It's an insidious little, I mean, heavy metal. Cadmium sits right below zinc on the periodic table and therefore shares many of its same chemical properties. In the environment it is distributed nearly everywhere we find zinc and therefore when we mine zinc, we consequently mine cadmium. When we galvanize (zinc treat) a nail or some other bit of steel, a little cadmium comes along for the ride. Think for a minute about how important galvanization is to the industrialized world. If you don't know, trust me, it's really important, and as such, this little bit of cadmium that comes along for the ride, becomes a lot of potential cadmium exposure. Add that to other avenues of exposure, like mines and metal processing along with the ease of cadmium uptake by agricultural crops, and we really are lucky our bodies have developed a system to attenuate the cadmium exposure in our diets. If not, a lot more of us might be saying Ouch ouch. So, how do our bodies do it? We take advantage of cadmium chemistry. The cadmium ion is positively charged and posses a large polarizability. Think of it like a water balloon with many electrons sloshing around from side to side. To a chemist, this is referred to as "soft (or B-type) lewis acid' behavior. These soft lewis acids prefer the company of soft lewis bases such as negatively charged (reduced) sulfur - aka sulfide. As cadmium gets absorbed by the human body it stimulates the production of the enzyme metallothionein which has an abundance of sulfide containing amino acids. Each metallothionein enzyme can sequester up to seven cadmium ions providing a fairly nice buffer against high cadmium intake. Those people who suffered from the ouch ouch disease just had too much cadmium in their diets which overwhelmed the sophisticated and elegant defense mechanism. I certainly don't want to give you the idea that cadmium has a completely chequered past. One of the things that makes cadmium so interesting is its many useful properties as well. To give cadmium its fair shake, you should know some of the most brilliant colours and paints result from cadmium salts and artists have taken advantage of these for years. Nickel-cadmium batteries show promise through higher efficiencies which will demonstrate their importance in the next generation of electric vehicles. Cadmium is an essential element in many forms of a new class of semi-conductor known as quantum dots. These advanced materials show promise in the areas of electronics, photo-voltaics and medical imaging. And finally in nature, a group at Princeton University a few years back showed that some marine diatons can substitute cadmium for zinc in the important enzyme carbonic anhydrase. This demonstrated that cadmium can be a nutrient as well. For we humans however, don't count on any nutritive value in cadmium, leave that to the dietons. Cadmium intake through contaminated foods or even tobacco smoking can lead to all kinds of problems, some even worse than the ouch-ouch disease. Chris Smith So the take home message is, don't eat your rechargeables. That was Steve Mylon with the story of cadmium, the chemical that keeps the world looking a nice range of colours. Next week, from colouring the world to changing it. Katherine Holt Tin cans, tin foil, tin whistles, tin soldiers.....these are that things that come to mind when we think of tin. Which is unfortunate, as tin cans are actually made from steel; tin foil is made from aluminium and tin whistles....well you get the idea. To be associated with a list of obsolete consumable items is especially unfortunate for tin, when we consider that it was responsible for literally changing civilisation! Have you heard of the Bronze Age? Chris Smith Well if not, do join Katherine Holt to find out how tin made it all happen 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.
