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Element Fact
Americium is one of the few radioactive elements that find its use in homes as a smoke detector.

Strontium, Sr

strontium sample

Atomic number: 38
Atomic mass: 87.62(1)
Natural abundance: 384 ppm
84Sr (83.913425) - 0.56%
86Sr (85.909262) - 9.86%
87Sr (86.908879) - 7.00%
88Sr (87.905614) - 82.58%

History and Production

Derived from the town in Scotland, Strontian. A mineral found in a lead mine near Strontian, Scotland in 1787 was shown to be a compound of a new element by A. Crawford in 1790. This was confirmed by T.C. Hope who distinguished the compounds of the alkaline earth metals from each other using flame colorations. Strontium was subsequently isolated by H. Davy in 1808 by electrolysis. The metal can be prepared by electrolysis of fused chloride with potassium chloride. It can also be produced by the reduction of strontium oxide with aluminium at a high temperature. The metal is used to make television tubes that improves the picture quality and also used to block the x-ray emission. The isotope 90Sr with long-lived beta emitter has potential uses as a power source for spacecrafts, navigational bouys and some other isolated entities where light-weight power sources are essential.

Physical Data

It is silvery white, lustrous and relatively soft metal. It quickly tainted with a yellow coloration due to the formation of the oxide when exposes to air. Strontium compounds also gives bright red flame coloration which can be distinguished from other alkaline earth metal compounds. The important ores are celestite (SrSO4) and strontianite (SrCO3).

Interatomic distance: 430.2 pm
Melting point: 777C
Boiling point: 1382C
Thermal conductivity/Wm-1K-1: 35.3 (27C)
Density/kgm-3: 2540 (20C), 2375 (m.p.)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 164.4 kJ/mol
Gibbs free energy of formation: 130.9 kJ/mol
Entropy: 164.6 J/mol K
Heat capacity: 20.8 J/mol K

Electronic data

Electronic configuration: [Kr] 5s2
Term symbol: 1S0
Electron affinity: 4.6313 kJ/mol   Electronegativity (Pauline): 0.95
Ionization energy (first, second, third): 549.475, 1064.25, 4138.26 kJ/mol

Chemical properties

Test for strontium:
(1) Flame test gives crimson color.
(2) Ammonium carbonate gives a white precipitate of strontium carbonate.
(3) Saturated calcium sulfate solution gives a white precipitate of strontium sulfate. This is a distinction test from calcium.

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