Strontium is a chemical element with the symbol Sr
and the atomic number 38. An alkaline earth metal,
strontium is a soft silver-white or yellowish metallic element that
is highly reactive chemically. The metal turns yellow when exposed
to air. It occurs naturally in the minerals celestine and
strontianite. The 90Sr isotope is present in radioactive
fallout and has a half-life of 28.90 years. Both strontium and
strontianite are named after Strontian, a village in Scotland near
which the mineral was first discovered.
What the mineral Strontium looks like.
Strontium is a grey, silvery metal that is softer than calcium
and even more reactive in water, with which it reacts on contact to
produce strontium hydroxide and hydrogen gas. It burns in air to
produce both strontium oxide and strontium nitride, but since it
does not react with nitrogen below 380 °C, at room temperature it
will only form the oxide spontaneously.
Because of its extreme reactivity with oxygen and water, this
element occurs naturally only in compounds with other elements,
such as in the minerals strontianite and celestite. It is kept
under a liquid hydrocarbon such as mineral oil or kerosene to
prevent oxidation; freshly exposed strontium metal rapidly turns a
yellowish color with the formation of the oxide. Finely powdered
strontium metal will ignite spontaneously in air at room
temperature. Volatile strontium salts impart a crimson color to
flames, and these salts are used in pyrotechnics and in the
production of flares. Natural strontium is a mixture of four stable
isotopes.
PERIODIC TABLE
Check out this interactive Periodic Table.
Check out this Strontium video. Prepared by The University of
Nottingham.