Periodic Table > Strontium


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.



A vertical column in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.

A horizontal row in the periodic table. The atomic number of each element increases by one, reading from left to right.

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.

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.

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.

Fact box

Group Melting point 777°C, 1431°F, 1050 K 
Period Boiling point 1377°C, 2511°F, 1650 K 
Block Density (g cm−3) 2.64 
Atomic number 38  Relative atomic mass 87.62  
State at 20°C Solid  Key isotopes 86Sr, 87Sr, 88Sr 
Electron configuration [Kr] 5s2  CAS number 7440-24-6 
ChemSpider ID 4514263 ChemSpider is a free chemical structure database


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.


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.

Uses and properties

Image explanation
The image is of a highly abstracted metallic ‘mushroom cloud’. It alludes to the presence of strontium in nuclear fallout.
A soft, silvery metal that burns in air and reacts with water.
Strontium is best known for the brilliant reds its salts give to fireworks and flares. It is also used in producing ferrite magnets and refining zinc.

Modern ‘glow-in-the-dark’ paints and plastics contain strontium aluminate. They absorb light during the day and release it slowly for hours afterwards.

Strontium-90, a radioactive isotope, is a by-product of nuclear reactors and present in nuclear fallout. It has a half-life of 28 years. It is absorbed by bone tissue instead of calcium and can destroy bone marrow and cause cancer. However, it is also useful as it is one of the best high-energy beta-emitters known. It can be used to generate electricity for space vehicles, remote weather stations and navigation buoys. It can also be used for thickness gauges and to remove static charges from machinery handling paper or plastic.

Strontium chloride hexahydrate is an ingredient in toothpaste for sensitive teeth.
Biological role
Strontium is incorporated into the shells of some deep-sea creatures and is essential to some stony corals. It has no biological role in humans and is non-toxic. Because it is similar to calcium, it can mimic its way into our bodies, ending up in our bones.

Radioactive strontium-90, which is produced in nuclear explosions and released during nuclear plant accidents, is particularly dangerous because it can be absorbed into the bones of young children.
Natural abundance
Strontium is found mainly in the minerals celestite and strontianite. China is now the leading producer of strontium. Strontium metal can be prepared by electrolysis of the molten strontium chloride and potassium chloride, or by reducing strontium oxide with aluminium in a vacuum.
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In 1787, an unusual rock which had been found in a lead mine at Strontian, Scotland, was investigated by Adair Crawford, an Edinburgh doctor. He realised it was a new mineral containing an unknown ‘earth’ which he named strontia. In 1791, another Edinburgh man, Thomas Charles Hope, made a fuller investigation of it and proved it was a new element. He also noted that it caused the flame of a candle to burn red.

Meanwhile Martin Heinrich Klaproth in Germany was working with the same mineral and he produced both strontium oxide and strontium hydroxide.

Strontium metal itself was isolated in 1808 at the Royal Institution in London by Humphry Davy by means of electrolysis, using the method with which he had already isolated sodium and potassium.

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.

Atomic data

Atomic radius, non-bonded (Å) 2.49 Covalent radius (Å) 1.90
Electron affinity (kJ mol−1) 4.631 Electronegativity
(Pauling scale)
Ionisation energies
(kJ mol−1)


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.


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

Oxidation states and isotopes

Common oxidation states 2
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  84Sr 83.913 0.56
  86Sr 85.909 9.86
  87Sr 86.909 7
  88Sr 87.906 82.58


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.


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.

Supply risk

Relative supply risk 8.6
Crustal abundance (ppm) 320
Recycling rate (%) <10
Substitutability Unknown
Production concentration (%) 83
Reserve distribution (%) 100
Top 3 producers
  • 1) China
  • 2) Spain
  • 3) Mexico
Top 3 reserve holders
  • 1) China
Political stability of top producer 24.1
Political stability of top reserve holder 24.1


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.

Pressure and temperature data – advanced

Specific heat capacity
(J kg−1 K−1)
306 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) Unknown
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
x 10-11
0.000429 1.134 121 - - - - - - -
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Listen to Strontium Podcast
Transcript :

Chemistry in its element: strontium


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, vegetarian gladiators, red fireworks and a mineral mistaken for barium; they are all under strontium's spotlight. Here's Richard Van Noorden.

Richard Van Noorden

In 1787, an intriguing mineral came to Edinburgh from a Lead mine in a small village on the shores of Loch Sunart, Argyll, in the western highlands of Scotland. At that time, the stuff was thought to be some sort of Barium compound. It was three year's later that Scott's Irish chemist, Adair Crawford, published a paper claiming that the mineral held a new species including a new chemical element. Other chemists, such as Edinburgh's Thomas Hope later prepared a number of compounds with the element, noting that it caused the candle's flame to burn red, while Barium compounds gave a green colour. And in 1808, Humphry Davy in London isolated the soft, silvery metal of the new element using electrolysis. The Scottish village was called Strontian, the mineral found there, strontianite and the new element strontium. So, it seems there never was an eminent professor, Stront, commemorated by element number 38.

Today, whenever you see a firework light up in brilliant crimson or a red flare smoking its way around a football stadium, you're looking at the light emitted from electrons transiting between energy levels in nitrate or carbonate salts as strontium. Strontium is most famous for that red glow in a flame, but as a metal it behaves like its reactive group II neighbours, beryllium, magnesium, calcium and barium. It's soft and silvery when freshly cut, but this sheen quickly turns yellow when exposed to air, as the metal readily reacts to form oxides; unlike other reactive alkaline earth metals, natural strontium is always found locked away in mineral compounds. Apart from the previously mentioned strontianite, which we know as strontium carbonate, there is also the beautiful sky blue celestite, strontium sulphate, which was discovered in Gloucestershire in 1799, where the locals were using it as gravel for paths in ornamental gardens.

Apart from colouring fireworks, we don't have much call nowadays for strontium compounds. Strontium carbonate notably is found in cathode ray tubes in old television sets. One of strontium's isotopes Strontium-90 has a more sinister reputation. It's a radioactive beta emitter, produced by nuclear fission with a half-life of 29 years. Created by nuclear tests from 1945 to the early 1970s, strontium-90 made its way from the air to grassland, cow stomachs, dairy products and as 1950's studies showed into children's milk teeth. It collects in bones too, being of a similar size to its group II neighbour, calcium ions. The nuclear reactor accident at Chernobyl in 1986 also threw strontium-90 into the air. Nowadays, it's used as a radioactive tracer in cancer therapy. Still strontium's close relation to calcium has made it a modern treatment for treating osteoporosis as the salt strontium ranelate, using non-radioactive isotopes, of course. Because strontium ions are roughly the same size as calcium ions, they bind tightly to calcium sensing receptors. It seems that this stimulates the formation of new bones and prevents old bone from being broken down.

And tracing strontium isotope levels in bone has allowed analytical chemists to come up with all sorts of conclusions about our past ancestor's diets, knowing that plants tend to be higher in natural strontium than meat. In 2007, for instance, Austrian researchers hit headlines by comparing strontium and zinc levels to support the hypothesis that Roman gladiators were vegetarians who ate mainly barley, beans and dried fruits.

Chris Smith

Chemistry World's Richard Van Noorden wrestling gladiator style with the story of strontium. Next time, we've heard of running through treacle, but what about this proposition.

Fred Campbell

Could a man walk across a swimming pool filled with Mercury? Don't ask me how the conversation had reached this point, but being surrounded by friends, who would, it is fair to say, describe themselves as science illiterate, I knew it was up to me, the token scientist around the table, to give the definitive answer. "No." I confidently said, adding rather smugly, "it is nowhere near dense enough." The next morning I was rudely awakened by my ringing mobile; not for the first time, I was wrong!

Chris Smith

And you can find out exactly how wrong Fred Campbell was at his dinner party when he unlocks the chemical secrets of quick silver, otherwise known as mercury on next week's Chemistry in its element. I hope you can join us. I'm Chris Smith, thanks for listening. Goodbye!


Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by There's more information and other episodes of Chemistry in its element on our website at

(End promo)
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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 :
A series of short experiments and demonstrations about the chemistry of light, taken from a lecture by Peter Wothers from the University of Cambridge
Description :
Assessment for Learning is an effective way of actively involving students in their learning.  Each session plan comes with suggestions about how to organise activities and worksheets that may be used...
Description :
In this experiment you will be looking to see whether precipitates form when you add drops of solutions of sulphates or carbonates to drops of solutions of group 1 or 2 metal ions.
Description :
A collection of visually stimulating and informative infographics about the elements, which would make a valuable addition to any science classroom.
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.

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Visual Elements images and videos
© Murray Robertson 2011.



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 3.0), 2010, National Institute of Standards and Technology, Gaithersburg, MD, accessed December 2014.
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

© John Emsley 2012.



Produced by The Naked Scientists.


Periodic Table of Videos

Created by video journalist Brady Haran working with chemists at The University of Nottingham.
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