Periodic Table > Calcium
 

Terminology


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


For more information on Murray Robertson’s image see Uses/Interesting 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 Melting point 842 oC, 1547.6 oF, 1115.15 K 
Period Boiling point 1484 oC, 2703.2 oF, 1757.15 K 
Block Density (kg m-3) 1530 
Atomic number 20  Relative atomic mass 40.078  
State at room temperature Solid  Key isotopes 40Ca 
Electron configuration [Ar] 4s2  CAS number 7440-70-2 
ChemSpider ID 4573905 ChemSpider is a free chemical structure database
 

Interesting Facts 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 / Interesting Facts

 
Image explanation

The spiral shell and bones reflect the essential presence of calcium in all living things.

Appearance

A silvery white, soft metal that tarnishes rapidly in air and reacts with water.

Source

Uses

Calcium metal is used as a reducing agent in preparing other metals such as thorium and uranium, and as an alloying agent for aluminium, beryllium, copper, lead and magnesium alloys. Calcium compounds are widely used. There are vast deposits of limestone (calcium carbonate) used directly as a building stone; when heated in kilns, this gives off carbon dioxide gas to leave quicklime (calcium oxide). This reacts vigorously with water to give slaked lime (calcium hydroxide). This is used to make cement, as a soil conditioner and in water treatment to reduce acidity, and in the chemicals industry. It has the advantage of being cheap and readily available. When mixed with sand it takes up carbon dioxide from the air and hardens as mortar and lime-plaster. Gypsum, calcium sulfate is the constituent of ordinary plaster, also used, as ‘plaster of Paris’, for setting bones.

Biological role

Calcium is essential to all living things, and calcium phosphate is the main component of bone. The average human contains about 1 kilogram of calcium. Children and pregnant women are encouraged to eat foods rich in calcium, such as milk and milk products, leafy green vegetables, fish and nuts and seeds, to promote the growth of healthy teeth and bones.

Natural abundance

Calcium is the fifth most abundant metal in the Earth’s crust, greater than 3% by mass. It is not found uncombined in nature, but occurs abundantly as limestone (calcium carbonate), gypsum (calcium sulfate), fluorite (calcium fluoride) and apatite (calcium chloro- or fluoro-phosphate). Calcium is prepared commercially by the electrolysis of fused calcium chloride to which calcium fluoride is added to lower the melting point.

 
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) 2.310 Covalent radius (Å) 1.74
Electron affinity (kJ mol-1) 2.368 Electronegativity
(Pauling scale)
1.000
Ionisation energies
(kJ mol-1)
 
1st
589.830
2nd
1145.446
3rd
4912.364
4th
6490.563
5th
8153.004
6th
10495.666
7th
12272.925
8th
14206.489
 

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 n/a
Crustal abundance (ppm) 41500
Leading producer China
Reserve base distribution (%) n/a
Production concentration (%) 65.20
Total governance factor(production) 8
Top 3 countries (mined)
  • 1) n/a
Top 3 countries (production)
  • 1) China
  • 2) USA
  • 3) India
 

Oxidation states/ 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 / Isotopes

 
Common oxidation states 2
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  40Ca 39.963 96.941 5.92 x 1021 EC-EC 
  42Ca 41.959 0.647
  43Ca 42.959 0.135
  44Ca 43.955 2.086
  46Ca 45.954 0.004 > 0.4 x 1016 β-β- 
  48Ca 47.953 0.187 4.3 x 1019 β-β- 
        > 7.1 x 1019 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 / Temperature - Advanced

 
Molar heat capacity
(J mol-1 K-1)
25.929 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) 17.2
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- 2.36
x 10-5
0.15 25.5 - - - - - - -
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History

Lime (calcium oxide, CaO) was the useful material obtained by heating limestone and used for centuries to make plaster and mortar. Antoine Lavoisier classified it as an ‘earth’ because it seemed impossible to reduce it further, but he suspected it was the oxide of an unknown element. In 1808, Humphry Davy tried to reduce moist lime by electrolysis, just as he had done with sodium and potassium, but he was not successful. So he tried a mixture of lime and mercury oxide and while this produced an amalgam of calcium and mercury, it was not enough to confirm that he’d obtained a new element.  (Jöns Jacob Berzelius had conducted a similar experiment and also obtained the amalgam.) Davy tried using more lime in the mixture and produced more of the amalgam from which he distilled off the mercury leaving just calcium.

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Podcasts

Listen to Calcium Podcast
Transcript :

Chemistry in Its Element - Calcium


(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 this week's Chemistry in its Element, I'm Chris Smith. This week it's the turn of the element that gives us cement, plaster of Paris, our own bones, hard teeth and hard water. 

Karen Faulds 

Milk, cheese, yogurt, spinach, almonds. What element do they all have in common? It's calcium of course! But whilst most off us immediately think of food when someone mentions calcium (and I personally hold the old milk TV adverts accountable for this), it actually has a far bigger role in our lives than that. Calcium is all around us. The average human contains approximately 1kg of calcium, of which 99% is stored in our bones. It is the 5th most abundant element in the earth's crust, occurring widely as calcium carbonate which is more commonly known as limestone. It is also the fifth most abundant dissolved ion in seawater. 

Calcium was named after the Latin term calx meaning lime, and is a reactive silvery metallic element found in Group 2 of the periodic table. It was first isolated in 1808 in England when Sir Humphry Davy electrolyzed a mixture of lime and mercuric oxide. Today we obtain calcium through the electrolysis of a fused salt such as calcium chloride. Once exposed to air, elemental calcium rapidly forms a grey-white oxide and nitride coating. Unlike magnesium, calcium is quite difficult to ignite, but once lit, it burns with a brilliant high-intensity red flame. 

The compounds of calcium are however much more useful than the element itself. Literature dating back to 975 AD shows that plaster of Paris (which is calcium sulphate) was used even then for setting broken bones. Calcium oxide (also known as lime or quicklime) is a major component of mortar and cement. The production of cement using calcium oxide has long been known; it was used by the Romans and also the Egyptians who built the Great Pyramid of Giza and Tutankhamen's tomb. Calcium fluoride is also well known for being insoluble and transparent over a wide range of wavelengths, making it useful for making cells and windows for infrared and ultraviolet spectrometers.

Our drinking water also contains calcium ions - more so in so called hard water areas. Hard water is the term used for water with a high proportion of calcium and magnesium (2 plus) ions. The calcium usually enters the water as it flows past either calcium carbonate, from limestone and chalk, or calcium sulfate, from other mineral deposits. Whilst some people do not like the taste, hard water is generally not harmful to your health. Although it does make your kettle furry! Interestingly, the taste of beer (something dear to my heart) seems related to the calcium concentration of the water used, and it is claimed that good beer should have a calcium concentration that is higher than that of hard tap water. 

Calcium is what is known as an essential element, meaning that it is an element which is absolutely necessary for life processes. Which is what the old milk TV adverts were trying to tell us after all. Calcium is used to produce the minerals contained in bones, shells and teeth through a process called biomineralisation. Calcium phosphate (also known as hydroxyapatite) is the mineral component of bones and teeth and is a particularly good example of how organisms fabricate 'living' composite materials. Indeed, the different properties (such as stiffness) of bone are produced by varying the amount of organic component, mostly a fibrous protein called collagen, with which hydroxyapatite is associated. The bone in our body functions not only as a structural support, but also as the central Ca store. Thus, during pregnancy, bones tend to be raided for their Ca in a process called demineralisation. Bone does not last forever; a serious medical problem is osteoporosis which is the decalcification of bone. This loss of bone mass which occurs with increasing age makes bones more susceptible to breaking under stress and it occurs mainly in older people, especially women. 

Calcium ions also play a crucial role in higher organisms as an intracellular messenger. Fluxes of Ca2+ trigger enzyme action in cells in response to receiving a hormonal or electrical signal from elsewhere in the organism. Calcium is also very important in helping blood to clot. When bleeding from a wound suddenly occurs, platelets gather at the wound and attempt to block the blood flow. Calcium, vitamin K, and a protein called fibrinogen help the platelets to form a clot. If your blood is lacking calcium or one of these other nutrients, it will take longer than normal for your blood to clot. 

The ability to detect extremely small amounts of an element can be a very useful adaptation for an animal if that element is important to it. For example, hermit crabs, which inhabit second hand shells and change to newer, bigger shells as they grow, have the ability to recognise shells suitable for occupation not only by feeling for them, but apparently also by measuring the minute amount of calcium carbonate that is dissolved in the water around a shell. They can readily distinguish natural shells containing calcium carbonate from calcium-bearing replicas made from calcium sulphate. The concentration of calcium detected by the hermit crab is in the order of 4ppm or less, which is amazingly low. 

So from strong teeth and bones, through to good tasting beer and ensuring hermit crabs find their perfect home -you can see that calcium really is an essential element. 

Chris Smith 

Well, I'm very at home with my hard water, and the local beer tastes quite good too, although I do get through quite a few kettles - indeed Russell Hobbs probably owe their buoyant share price just down to me. Well, maybe. That was Strathclyde University's Karen Faulds with the story of Calcium. Next week, if you were an element which one would you be? 

Pat Bailey 

If I had to choose a person to represent gold, then I guess it might be an ambitious young stockbroker, a bit flashy, and not great at forming relationships. For helium - an airy-fairy blonde with a bit of a squeaky voice, but with aspirations to join the nobility. And for boron? Well at first glance a boring, middle-aged accountant, maybe wearing brown corduroys and a tweed jacket . but with an unexpected side-to him in his spare time - skydiving, and a member of a highly dubious society that indulges in swapping partners. 

Chris Smith 

And you can get the inside story on Boron's swinging antics with Pat Bailey in 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 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 :
In this experiment you will be observing and interpreting the changes when drops of solutions of various anions are added to drops of solutions of Group 2 element cations.
Description :
Metals in Group 2 of the Periodic Table are less reactive than those in Group 1. This experiment indicates the relative reactivity of elements within the group.
Description :
Many elements react with oxygen on heating. These reactions and the properties of their products illustrate the periodic nature of the elements.
Description :
Calcium carbonate is strongly heated until it undergoes thermal decomposition to form calcium oxide and carbon dioxide. The calcium oxide (unslaked lime) is dissolved in water to form calcium hydroxi...
Description :
Limestone and chalk are mainly calcium carbonate. In this experiment, calcium carbonate is heated to form calcium oxide. This is reacted with a few drops of water, and the resulting calcium hydroxide...
Description :
Many elements react with chlorine on heating. The reactions and the properties of the products illustrate the periodic nature of the elements. The reactions require less energy input to initiate than...
 

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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.