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38Sr87.62

Element 38, an alkaline earth metal

Strontium

The element that makes fireworks red, named after a village in the Scottish Highlands.

At a glance

Symbol
Sr
Atomic number
38
Average atomic mass
87.62
Group
2
Period
5
Family
alkaline earth metal
Electron configuration
[Kr] 5s²
Valence electrons
2
Electronegativity
0.95
Common ions
Sr²⁺
Isotopes
four stable isotopes, mostly ⁸⁸Sr; radioactive ⁹⁰Sr from nuclear fallout is dangerous because the body stores it in bone as if it were calcium

On the table

Periodic table with Strontium highlighted123456789101112131415161718123456757-7189-103HHeLiBeBCNOFNeNaMgAlSiPSClArKCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXeCsBaLaCePrNdPmSmEuGdTbDyHoErTmYbLuHfTaWReOsIrPtAuHgTlPbBiPoAtRnFrRaAcThPaUNpPuAmCmBkCfEsFmMdNoLrRfDbSgBhHsMtDsRgCnNhFlMcLvTsOg

Period 5, group 2. The other alkaline earth metals are tinted, and every cell opens its own article.

Electrons and bonding

Sr

Two valence electrons, which strontium gives up to form the Sr²⁺ ion in its compounds.

Properties

State at 25 °C
solid
What it looks like
soft, silvery-white metal that yellows in air
Melting point
777 °C
Boiling point
1382 °C
Density
2.64 g/cm³
Flame test
crimson red

Where it is found

Mined as celestine (SrSO₄), mostly in Spain, China and Mexico, and as strontianite (SrCO₃).

Discovery and name

Adair Crawford and William Cruikshank recognized in 1790 that a mineral from the lead mines at Strontian, Scotland, contained a new earth. Humphry Davy isolated the metal in 1808 by electrolysis.

What it is used for

Red fireworks and emergency flares, glow-in-the-dark paints and toys (strontium aluminate), ferrite magnets in small motors and speakers, and toothpaste for sensitive teeth. It was once added to the glass of television tubes to block X-rays, and strontium clocks are among the most precise clocks ever built.

In compounds

Sr(NO₃)₂strontium nitrate, red fireworksSrCO₃strontianiteSrSO₄celestineSrAl₂O₄strontium aluminate, glow-in-the-darkSrCl₂strontium chloride, in toothpaste