Strontium

Symbol SrAtomic 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

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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 mineral Bensonite.

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.

Atomic dataNuclear data
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Chemistry concepts

Reference
Pauling
 
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Strontium Nuclear Data

Z
A
Atomic
Mass (u)
Nuclear
Mass(GeV/c2
Binding
Energy(MeV)
Spin
Natural
Abund.
Half-life
Decay
Q
MeV
38
84
83.913430
78.1461
728.91
0
0.0056
stable
...
...
38
85
84.912937
79.0771
737.44
9/2
...
64.8d
b+
1.08
38
86
85.909267
80.0052
748.93
0
0.0986
stable
...
...
38
87
86.908884
80.9363
757.36
9/2
0.07
stable
...
...
38
88
87.905619
81.8648
768.47
0
0.8258
stable
...
...
38
90
89.907738
83.7298
782.64
0
...
29y
b-
0.55

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.

Atomic data
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Reference
Rohlf
 
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