Periodic Table > Magnesium
 

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 Melting point 650 oC, 1202 oF, 923.15 K 
Period Boiling point 1090 oC, 1994 oF, 1363.15 K 
Block Density (kg m-3) 1738 
Atomic number 12  Relative atomic mass 24.305  
State at room temperature Solid  Key isotopes 24Mg 
Electron configuration [Ne] 3s2  CAS number 7439-95-4 
ChemSpider ID 4575328 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 image reflects the importance of the single atom of Magnesium present in the organic molecule of chlorophyll which enables the process of photosynthesis to take place.

Appearance

A silvery white metal that can be made to burn with a bright light.

Uses

Magnesium is used in flares, pyrotechnics and incendiary bombs and was formerly used in flash bulbs. As it is one-third less dense than aluminium, its alloys are useful in aeroplane and missile construction and in alloys to provide lightweight frames for bicycles, car seats and luggage. It improves the mechanical, fabrication and welding characteristics of aluminium when used as an alloying agent. Grignard reagents, which are organic magnesium compounds, are important commercially.

Biological role

Magnesium is an essential element in both plant and animal life. It is non-toxic. Chlorophylls are magnesium-centred porphyrins, so, without magnesium, photosynthesis, and therefore life as we know it, would not exist. Humans take in 250-350 milligrams each day (about 100 grams a year), and we each have about 20 grams in our bodies. Magnesium hydoxide (milk of magnesia), sulphate (Epsom salts), chloride and citrate are used in medicine.

Natural abundance

Magnesium is the eighth most abundant element in the Earth’s crust, but does not occur uncombined. It is found in large deposits in minerals such as magnesite and dolomite. The sea contains trillions of tonnes of magnesium, and this is the source of much of the 300,000 tonnes now produced annually. It is prepared by electrolysis of fused magnesium chloride derived from brines, wells and sea water.

 
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) 1.730 Covalent radius (Å) 1.4
Electron affinity (kJ mol-1) Not stable Electronegativity
(Pauling scale)
1.310
Ionisation energies
(kJ mol-1)
 
1st
737.749
2nd
1450.682
3rd
7732.686
4th
10542.510
5th
13630.472
6th
18019.587
7th
21711.113
8th
25661.219
 

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) 28104
Leading producer China
Reserve base distribution (%) n/a
Production concentration (%) 61.80
Total governance factor(production) 9
Top 3 countries (mined)
  • 1) China
  • 2) N. Korea
  • 3) Russia
Top 3 countries (production)
  • 1) China
  • 2) Russia
  • 3) Turkey
 

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
  24Mg 23.985 78.99
  25Mg 24.986 10
  26Mg 25.983 11.01
 

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)
24.869 Young's modulus (GPa) 44.7
Shear modulus (GPa) 17.3 Bulk modulus (GPa) 44.7
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
6.53
x 10-9
1.52
x 10-2
21.5 - - - - - - - -
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History

The first person to recognise that magnesium was an element was Joseph Black at Edinburgh in 1755. He distinguished magnesia (magnesium oxide, MgO) from lime (calcium oxide, CaO) although both were produced by heating similar kinds of carbonate rocks, magnesite and limestone respectively. Another magnesium mineral called meerschaum (magnesium silicate) was reported by Thomas Henry in 1789, who said that it was much used in Turkey to make pipes for smoking tobacco.


An impure form of metallic magnesium was first produced in 1792 by Anton Rupprecht who heated magnesia with charcoal. A pure, but tiny, amount of the metal was isolated in 1808 by Humphry Davy by the electrolysis of magnesium oxide. However, it was the French scientist, Antoine-Alexandre-Brutus Bussy who made a sizeable amount of the metal in 1831 by reacting magnesium chloride with potassium, and he then studied its properties.

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Podcasts

Listen to Magnesium Podcast
Transcript :

Chemistry in Its Element - Magnesium


  (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 meet the substance whose chemical claim to fame is that its quite literally hit a bum note in the past as a cure for constipation.    But its explosive role isn't just confined to the colon because it's also the basis of incendriary bombs and even the existence of life on earth.   And to tell the story of Magnesium, here's John Emsley.

 

John Emsley

 

It was once the destroyer of cities - now it's a saver of energy

The summer of 1618 saw England gripped by drought, but as Henry Wicker walked across Epsom Common he was came across a pool of water from which thirsty cattle refused to drink. He found that the water tasted bitter and on evaporation it yielded a salt which had a remarkable effect: it acted as a laxative. This became the famous Epsom's salt (magnesium sulfate, MgSO4) and became a treatment for constipation for the next 350 years. 

The first person to propose that magnesium was an element was Joseph Black of Edinburgh in 1755, and an impure form of metallic magnesium was produced in 1792 by Anton Rupprecht who heated magnesia (magnesium oxide, MgO) with charcoal. He named the element austrium after his native Austria. A small sample of the pure metal was isolated by Humphry Davy in 1808, by the electrolysis of moist MgO, and he proposed the name magnium based on the mineral magnesite (MgCO3) which came from Magnesia in Greece. Neither name survived and eventually it was called magnesium.

Magnesiumis essential to almost all life on Earth - it is at the heart of the chlorophyll molecule, which plants use to convert carbon dioxide into glucose, and then to cellulose, starch, and many other molecules which pass along the food chain. Humans take in around 300 mg of magnesium per day and we need at least 200 mg, but the body has a store of around 25 g of this element in its skeleton so there is rarely a deficiency.

Almonds, brazil nuts, cashew nuts, soybeans, parsnips, bran, and even chocolate are all rich in magnesium. Some brands of beer contain a lot, such as Webster's Yorkshire Bitter - it may owe some of its flavour to the high levels of magnesium sulfate in the water used to brew it.

Magnesium is the seventh most abundant element in the Earth's crust, and third most abundant if the Earth's mantle is also taken into consideration because this consists largely of olivine and pyroxene, which are magnesium silicates. It is also abundant in sea water (1200 p.p.m.) so much so that this was the source of magnesium for bombs in World War II. The metal itself was produced by the electrolysis of the molten chloride.

Once magnesium starts to burn it is almost impossible to extinguish, because it reacts exothermically with oxygen, nitrogen and water. It burns with a bright light and was used for photographic flash bulbs It made an ideal incendiary agent and in some air raids during World War II as many as half a million 2 kg magnesium bombs would be scattered over a city in the space of an hour. The result was massive conflagrations and firestorms. Bulk magnesium metal is not easily ignited so this had to be done by a thermite reaction at the heart of the bomb. The thermite reaction, between aluminium powder and iron oxide, releases more than enough heat to cause the magnesium casing of the bomb to burn fiercely.

Many minerals are known which contain magnesium; but the main ones are dolomite (calcium magnesium carbonate, CaMg(CO3)2) and magnesite which are mined to the extent of 10 million tonnes per year. Magnesite is heated to convert it to magnesia (MgO), and this has several applications: fertilizers; cattle feed supplement; a bulking agent in plastics; and for heat-resistant bricks for fireplaces and furnaces. 

The metal itself is being produced in increasing amounts. It was originally introduced for racing bicycles which were the first vehicles to use pure magnesium frames, giving a better combination of strength and lightness than other metals. (A steel frame is nearly five times heavier than a magnesium one.) 

For use as a metal, magnesium is alloyed with a few percent of aluminium, plus traces of zinc and manganese, to improve strength, corrosion resistance and welding qualities, and this alloy is used to save energy by making things lighter. It is found in car and aircraft seats, lightweight luggage, lawn mowers, power tools, disc drives and cameras. At the end of its useful life the magnesium in all these products can be recycled at very little cost. Because it is an electropositive metal, magnesium can be act as a 'sacrificial' electrode to protect iron and steel structures because it corrodes away preferentially when they are exposed to water which otherwise would cause rusting

 

 

Chris Smith

So better bikes, better bombs and better bums.   Thank you very much to science writer John Emsley for telling the tale of Magnesium.   Next week the illuminating story of the element that spawned a light bulb but really needs to work on its image.

Quentin Cooper

If any element needs a change of PR this is the one.    It's brittle, prone to ponginess and arguably the dunce of the periodic table.   Even the man who discovered osmium treated it rather sniffily.     It reeked - or at least some of its compounds did.   Tennant described the "pungent and penetrating smell"  as one of the new element's "most distinguishing characters".    So he called it osmium - osme being the Greek for odour.

 

Chris Smith

That's Quentin Cooper who will be undressing Osmium for us in next week's Chemistry in its Element, I hope you can join us.   I'm Chris Smith, thank you for listening, see you next time. 

(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 :
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 :
Find out why chalk - calcium or magnesium carbonate - is as important in weightlifting as it is in tennis, rock climbing, and even fire-fighting.
Description :
This experiment illustrates a reaction with low activation energy. Magnesium reacts with silicon to produce magnesium silicide. This then decomposes in dilute acid to produce silane, which spontaneou...
Description :
Burning magnesium ribbon is plunged into the steam above boiling water in a conical flask. In the first method, the hydrogen that is formed is allowed to burn at the mouth of the flask. In the second...
 

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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.