Strontium (Sr)

Strontium behaves chemically like calcium, which is the whole problem with strontium-90: fallout from atmospheric nuclear testing was taken up into bone and teeth as if it were calcium, and the "baby tooth survey" of the early 1960s measured it in children's milk teeth well enough to help push through the Partial Test Ban Treaty. That same chemistry makes it useful — strontium ions substituting into bone mineral is why it was prescribed for osteoporosis. Strontium salts give the purest red in pyrotechnics; nothing else comes close.

Properties

Atomic number

38

Symbol

Sr

Standard atomic weight

87.62 u

Category

Alkaline earth metal

Group

2

Period

5

Block

s-block

Electron configuration

[Kr] 5s²

Electrons per shell

2, 8, 18, 8, 2

Melting point

1,050 K — 776.9 °C — 1430.3 °F

Boiling point

1,655 K — 1381.8 °C — 2519.3 °F

Density

2.64 g/cm³

Electronegativity

0.95 (Pauling)

Oxidation states

+2

Discovered

1790 by Adair Crawford; isolated by Humphry Davy in 1808

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s²

Noble gas shorthand

[Kr] 5s²

Shells

K: 2 · L: 8 · M: 18 · N: 8 · O: 2

What it is used for

• The red in fireworks, road flares and tracer rounds
• Strontium ranelate for osteoporosis, in some countries
• Strontium aluminate in glow-in-the-dark paint and exit signs
• Strontium-90 as a heat source in remote thermoelectric generators
• Ferrite magnets in loudspeakers and small motors

Hazards

• Strontium-90 is a bone-seeking beta emitter with a 28.8-year half-life

Named after Strontian, a village in the Scottish Highlands where the mineral strontianite was found — the only chemical element named after a place in the British Isles.

Neighbours in the table

Group 2

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Strontium sits in group 2 with beryllium, magnesium, calcium, barium, radium.