Strontium Facts (Atomic Number 38 or Sr)

Strontium is a yellowish-white alkaline earth metal with atomic number 38 and element symbol Sr. The element is known for producing red flames in fireworks and emergency flares and for its radioactive isotope that is found in nuclear fallout. Here is a collection of strontium element facts.

Strontium Basic Facts

There are 20 known isotopes of strontium, 4 stable and 16 unstable. Natural strontium is a mixture of the 4 stable isotopes.

Properties: Strontium is softer than calcium and decomposes more vigorously in water. Finely divided strontium metal ignites spontaneously in air. Strontium is a silvery metal, but it rapidly oxidizes to a yellowish color. Because of its propensity for oxidation and ignition, strontium is typically stored under kerosene. Strontium salts color flames crimson and are used in fireworks and flares.

Uses: Strontium-90 is used in Systems for Nuclear Auxilliary Power (SNAP) devices. Strontium is used in producing glass for color television picture tubes. It is also used to produce ferrite magnets and to refine zinc. Strontium titanate is very soft but has an extremely high refractive index and an optical dispersion greater than that of diamond.

Element Classification: Alkaline earth metal

Biological Role: Radiolarian protozoa belonging to the group Acantharea make their skeletons of strontium sulfate. In vertebrates, strontium replaces a small amount of calcium in skeletons. In humans, absorbed strontium is primarily deposited in bones. In adults, the element only attaches to bone surfaces, while it can replace calcium in growing bones of children, potentially leading to growth problems. Strontium ranelate can increase bone density and reduce the incidence of fractures, but it also increases the risk of cardiovascular problems. Topically applied strontium inhibits sensory irritation. It is used in some toothpastes to reduce sensitivity. While stable strontium isotopes present no significant health threat, the radioisotope strontium-90 is considered dangerous. Like the stable isotopes, it is absorbed into bones. However, it undergoes beta-minus decay and thus poses a radiation hazard.

Strontium Physical Data

• Density (g/cc): 2.54
• Melting Point (K): 1042
• Boiling Point (K): 1657
• Appearance: Silvery, malleable metal
• Atomic Radius (pm): 215
• Atomic Volume (cc/mol): 33.7
• Covalent Radius (pm): 191
• Ionic Radius: 112 (+2e)
• Specific Heat (@20°C J/g mol): 0.301
• Fusion Heat (kJ/mol): 9.20
• Evaporation Heat (kJ/mol): 144
• Pauling Negativity Number: 0.95
• First Ionizing Energy (kJ/mol): 549.0
• Oxidation States: 2
• Lattice Structure: Face-Centered Cubic

Sources

• Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
• Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
• Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.