Strontium

Symbol

Sr

Atomic number

38

Atomic mass	87.62		Thermal conductivity	0.353
Atomic radius	2.45		Covalent radius	1.91
Density	2.6		Atomic volume	33.7
Melting point	1041		Oxidation states	2
Boiling point	1650		Stable isotopes	4
Heat of vapor.	144.0		Electronegativity	0.95
Heat of fusion	8.30		First ionization	5.695
Specific heat	0.30		Electrical conduct.	...

Electron configuration

Strontium

Strontium is a metal, but as such has found little practical use. Most of its compounds are similar to those of calcium.

Strontium nitrate Sr(NO₃)₂ is mixed with carbon and sulfur to make red fire for use in fireworks, flares, and signal shells. Strontium chlorate, Sr(ClO₃)₂ can be used for the same purpose. One mineral form of strontium is a crystalline form of strontium sulfate called celestite. Others include the carbonate minerals strontianite and Weloganite. Strontium appears in the carbonate mineral Bensonite.

Strontium appears with boron in the oxide mineral tunellite and with barium in the silicate minerals Brewsterite and heulandite.

The radioisotope strontium-90 has been problematic in the fallout from nuclear weapons testing and nuclear accidents. Its intermediate halflife makes it quite radioactive, and since its compounds mimic those of calcium, it is taken up and reconcentrated in living organisms.

Strontium Nuclear Data

The isotopes of strontium have an important role in geologic dating. The rubidium/strontium dating method uses the two isotopes ⁸⁷Sr and ⁸⁶Sr. The ⁸⁶Sr is non-radiogenic in origin and is presumed to remain constant in the earth's minerals. The ⁸⁷Sr is comparable in abundance at the present time, but ⁸⁷Rb produces ⁸⁷Sr with a half-life of 48.8 x 10⁹ years. Plotting the ratios of ⁸⁷Rb and ⁸⁷Sr to ⁸⁶Sr in a rock sample allows you to correct for the original concentration and allows you to detect the loss of one of the members of the process. It is therefore one of the processes of choice in estimating the age of the earth.

Strontium-90 is one of the most dangerous of the radioactive fission fragments from nuclear fission since it has a relatively short half-life (29 yr) and tends to be taken up by living organisms. Vertibrates which need calcium will take up strontium-90 since it is so chemically similar to calcium, and it will therefore remain in bones and teeth to be a continuing source of ionizing radiation. It was one of the most troublesome constituents of the fallout from nuclear weapons testing.