Strontium · element 38
A Scottish village's metal that paints fireworks crimson, glows in the dark and reveals where ancient people grew up
Key facts
Strontium is the only element named after a place in the United Kingdom. The lead mines at Strontian, a small village on the west coast of the Scottish Highlands, produced an unusual mineral in the 1780s, and the metal inside it was named accordingly. It is a soft, silvery alkaline earth metal that behaves so much like calcium that the human body cannot tell them apart.
That likeness cuts both ways. Stable strontium is harmless and has even been used in toothpaste and osteoporosis drugs. Radioactive strontium-90, produced in nuclear explosions and reactors, is dangerous precisely because bones take it up as though it were calcium. In between lie the everyday uses: the crimson of flares and fireworks, fridge magnets and glow-in-the-dark stars on bedroom ceilings.
Where it is found
Strontium is more abundant in the crust than carbon, at roughly 370 parts per million, but it is spread through calcium-bearing rocks rather than forming rich deposits. Two minerals are mined: celestine, a strontium sulfate that often forms pale blue crystals, and strontianite, the carbonate from the original Scottish locality. Spain, China, Mexico and Iran are the main producers.
Seawater contains about 8 milligrams of strontium per litre, and corals and shellfish build it into their skeletons. Because the ratio of strontium isotopes in rocks varies from region to region, and because plants and animals pick up the local ratio, strontium in teeth and bones records where a person or animal lived while those tissues formed. Archaeologists use this to trace prehistoric migration.
How it was discovered
In 1790 the Irish chemist Adair Crawford, working with William Cruickshank, examined a mineral from Strontian that had been mistaken for a barium ore. Its salts behaved differently from those of barium, and Crawford suggested it contained a new earth. Thomas Charles Hope in Edinburgh confirmed this over the next few years and noted that its compounds turned a flame brilliant crimson.
The metal itself was first isolated in 1808 by Humphry Davy in London, who passed an electric current through moist strontium hydroxide mixed with mercury oxide and drove off the mercury. The same year Davy isolated calcium, barium and magnesium by the same method.
What we use it for
For decades the biggest use of strontium was one nobody saw. The glass faceplates of colour television tubes contained strontium oxide to absorb the X-rays generated inside, and every cathode ray television and monitor carried several hundred grams of it. When flat screens replaced them that market vanished almost overnight.
Today strontium goes into ceramic ferrite magnets for motors, loudspeakers and fridge doors, and into strontium nitrate and carbonate for the red of fireworks, distress flares and road flares. Strontium aluminate doped with europium is the modern glow-in-the-dark pigment, far brighter and longer lasting than the old zinc sulfide paints and completely non-radioactive. Strontium chloride is used in toothpastes for sensitive teeth, and strontium-89 is given to relieve pain from cancer that has spread to bone.
Reading the numbers
Strontium melts at 777 °C and boils at 1377 °C, moderate figures for a metal and lower than calcium's melting point. Its density of 2.64 grams per cubic centimetre is almost exactly that of aluminium, so it is light for a metal but still sinks in water, unlike its group 1 neighbour rubidium, which is even lighter.
The configuration [Kr] 5s2 gives two electrons in the outer shell, and strontium loses both to form Sr2+. The first two ionisation energies, 549.5 and 1064.2 kJ/mol, are modest, while the third leaps to 4138 kJ/mol because it would have to break into the full shell beneath. That pattern is the signature of a group 2 element. Electronegativity of 0.95 is low, close to calcium's 1.00. Strontium sits directly beneath calcium, and the two ions are so similar in size and charge that strontium substitutes for calcium in minerals, shells and bones.
Safety and the environment
Strontium metal reacts with water and must be kept under oil, but its common compounds are low in toxicity and were used for years in toothpaste and glass. The concern is strontium-90, a fission product with a half-life of about 29 years that emits beta radiation. Deposited in bone, it can damage marrow and cause leukaemia. Fallout from atmospheric weapons tests in the 1950s and 1960s spread it worldwide, and the Chernobyl accident released more.
A famous survey of children's baby teeth in St Louis from the late 1950s showed strontium-90 levels rising with each year of testing. The findings helped build public support for the 1963 treaty that banned nuclear tests in the atmosphere.
Did you know?
- Strontium is the only element named after a place in the United Kingdom: Strontian, a village in the Scottish Highlands.
- A survey of baby teeth in St Louis found strontium-90 from nuclear tests rising year by year, which helped bring about the 1963 Partial Test Ban Treaty.
- The glow-in-the-dark stars on bedroom ceilings are usually strontium aluminate, which replaced radioactive radium paint.
- The ratio of strontium isotopes locked in a person's tooth enamel reveals the region where they lived as a child.
- Before flat screens, the glass of colour television tubes consumed most of the world's strontium to block X-rays.
- Strontium compounds give fireworks and emergency flares their deep crimson colour.
More in the alkaline earth metals
These share a column with strontium, so their outer electrons are arranged in a similar way and they tend to behave alike.
See all 6 alkaline earth metals on one page, or browse all 118 elements.
Compare Strontium with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
Is strontium radioactive?
Natural strontium is not radioactive; it consists of four stable isotopes. Strontium-90 is a radioactive isotope made by nuclear fission and does not occur naturally. It was spread by weapons tests and the Chernobyl accident and is dangerous because bones absorb it like calcium.
Why does strontium burn red?
When strontium compounds are heated in a flame, electrons in strontium atoms and ions jump to higher energy levels and then fall back, giving off light at specific wavelengths. For strontium those wavelengths lie in the red part of the spectrum, producing a crimson colour. Fireworks makers rely on this, just as they use barium for green and copper for blue.
Is strontium good for bones?
Stable strontium is chemically similar to calcium and is taken up by bone. A prescription drug, strontium ranelate, was used to treat osteoporosis but its use has been restricted because of heart risks. Strontium supplements sold over the counter are not proven to be safe or effective, and radioactive strontium-90 is harmful to bone.
What is strontium used for?
Its main uses are in ceramic ferrite magnets, in red pyrotechnics and flares, and in glow-in-the-dark pigments. Smaller amounts go into toothpaste for sensitive teeth, zinc refining and specialist glass. Radioactive isotopes are used in medicine and in heat sources for remote equipment.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Strontium reference article. Spotted an error? Tell us.