Periodic Table > Cadmium
 

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 12  Melting point 321.069 oC, 609.924 oF, 594.219 K 
Period Boiling point 767 oC, 1412.6 oF, 1040.15 K 
Block Density (kg m-3) 8647 
Atomic number 48  Relative atomic mass 112.411  
State at room temperature Solid  Key isotopes 114Cd 
Electron configuration [Kr] 4d105s2  CAS number 7440-43-9 
ChemSpider ID 22410 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 alchemical symbol used here was once used to represent “earth” elements. Cadmium is a natural element in the earth's crust.
Appearance
A silvery metal produced as a by-product of zinc refining. It is used in rechargeable batteries, and cadmium sulfide was once a common pigment known as cadmium yellow. Cadmium accumulates in the body; although a person’s daily intake may be as little as 0.05 milligrammes, he or she will have stored on average about 50 milligrammes. Cadmium is a poison and is known to cause birth defects and cancer. As a result, there are moves to limit its use.
Uses
Cadmium is used extensively in electroplating, which accounts for about 60% of its use. It is also used in many types of solder, for standard e.m.f. cells, for nickel-cadmium batteries and in rods to control atomic fission. It is a component of some of the lowest melting alloys, alloys with low coefficients of friction, and alloys with great resistance to fatigue. Cadmium compounds are used in blue and green phosphors in colour television sets. Cadmium forms a number of compounds, the sulfide being used as an artist’s pigment as it is bright yellow.
Biological role
Cadmium is toxic, carcinogenic and teratogenic and accumulates in the body. In the past, failure to recognise the toxicity of this element caused workers to be exposed to danger in the form of solder fumes and cadmium plating baths.
Natural abundance
The only mineral containing significant quantities of cadmium is greenockite, although some is present in sphalerite. Almost all commercially produced cadmium is obtained as a by-product of the treatment of zinc, copper and lead ores.
 
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) 2.180 Covalent radius (Å) 1.4
Electron affinity (kJ mol-1) Not stable Electronegativity
(Pauling scale)
1.690
Ionisation energies
(kJ mol-1)
 
1st
867.769
2nd
1631.403
3rd
3616.267
4th
-
5th
-
6th
-
7th
-
8th
-
 

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 5.5
Country with largest reserve base China
Crustal abundance (ppm) 0.08
Leading producer China
Reserve base distribution (%) 23.30
Production concentration (%) 34.80
Total governance factor(production) 6
Top 3 countries (mined)
  • 1) China
  • 2) Australia
  • 3) Kazakhstan
Top 3 countries (production)
  • 1) China
  • 2) S. Korea
  • 3) Japan
 

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 2
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  106Cd 105.906 1.25 > 1.9 x 1019 EC, EC 
  108Cd 107.904 0.89 > 4.1 x 1017 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 β-β- 
  114Cd 113.903 28.73 > 1.3 x 1018 β-β- 
  116Cd 115.905 7.49 3.8 x 1019 β-β- 
 

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)
26.02 Young's modulus (GPa) 49.9
Shear modulus (GPa) 19.2 Bulk modulus (GPa) 41.6
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
2.8
x 10-4
18.2 - - - - - - - - -
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History

In the early 1800s, the apothecaries of Hanover, Germany, made zinc oxide by heating a naturally occurring form of zinc carbonate called cadmia. Sometimes the product was discoloured instead of being pure white, and when Friedrich Stromeyer of Göttingen University looked into the problem he traced the discoloration to a component he could not identify, and which he deduced must be an unknown element. This he separated as its brown oxide and, by heating it with lampblack (carbon), he produced a sample of a blue-grey metal which he named cadmium after the name for the mineral. That was in 1817. Meanwhile two other Germans, Karl Meissner in Halle, and Karl Karsten in Berlin, were working on the same problem and announced their discovery of cadmium the following year.

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Podcasts

Listen to Cadmium Podcast
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 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 :
Assessment for Learning is an effective way of actively involving students in their learning. This is a series of plans based around chemistry topics.
Description :
When concentrated hydrochloric acid is added to a very dilute solution of copper sulfate, the pale blue solution slowly turns yellow-green on the formation of a copper chloride complex. When concentr...
Description :
The purpose of this experiment is to observe and interpret some of the chemistry of three first row transition elements and to compare them with a typical s-block element.
Description :
The Periodic Table allows chemists to see similarities and trends in the properties of chemical elements. This experiment illustrates some properties of the common transition elements and their compo...
Description :
In this experiment you will be looking at a group of transition elements chromium, molybdenum and tungsten.
Description :
The purpose of this experiment is to examine some of the solution chemistry of the transition elements.
 

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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.