Strontium (Sr)
“Every crimson-red burst in a firework show is strontium at work — a soft alkaline-earth metal named after a tiny Scottish mining village.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
The notes
Characteristics
- Electron configuration [Kr] 5s² — Period 5, Group 2, s-block alkaline earth metal; it happily sheds both valence electrons to become the Sr²⁺ ion.
- Reacts vigorously with cold water — Sr + 2H₂O → Sr(OH)₂ + H₂ — more fiercely than calcium, though less wildly than barium; hence the oil-bottle storage.
- Its volatile salts paint a flame intense crimson — the same light emission that puts the red into fireworks, flares and railway fuses.
- The radioactive isotope Sr-90 (half-life about 29 years) is born in nuclear fission, mimics calcium and lodges in bone — the most feared ingredient of fallout; yet injected Sr-89 chloride eases the pain of bone-cancer patients.
A soft, silvery-white metal with a pale golden tint where freshly cut. It is so anxious to react with air that lumps must be stored under mineral oil, and a polished surface loses its shine within minutes in the open.
Where you meet it
✦ Uses
- The red stars of fireworks — strontium nitrate and strontium carbonate are the colour-plus-oxygen duo behind every crimson burst, from Dhaka wedding parties to cricket-victory nights.
- Strontium ferrite (SrFe₁₂O₁₉) permanent magnets — cheap, rust-proof magnets inside loudspeakers, fridge magnets and the small motors of fans and toys.
- Strontium chloride in “sensitive-teeth” toothpastes — it plugs the exposed micro-tubules in tooth dentine that make cold water sting.
- Strontium aluminate (SrAl₂O₄) glow-in-the-dark pigment — the green afterglow on emergency exit signs, watch dials and children’s ceiling stars.
◍ Everyday examples
- The next red burst at a wedding, Eid fair or cricket-celebration fireworks show is almost certainly strontium salts burning above 2,000 °C.
- The luminous stars and stickers on a bedroom ceiling keep glowing minutes after the lights go off — strontium aluminate releasing stored daylight.
- Some sensitivity-relief toothpaste tubes on a pharmacy shelf openly list strontium chloride hexahydrate among their ingredients.
History & name
In 1787 quarrymen in the lead mines of Strontian, a Highland village in western Scotland, pulled out a heavy mineral nobody could classify. In 1790 the Irish chemist Adair Crawford showed that this “strontianite” refused to behave like the barium minerals it resembled, and Thomas Charles Hope of Edinburgh soon confirmed a brand-new “earth” — its crimson flame was the giveaway. The metal itself waited until 1808, when Humphry Davy isolated it by electrolysis. Strontium thus became the only element in the periodic table named after a place in Scotland.