Overview

Strontium is a member of the alkaline earth metals. The alkaline earth metals make up Group 2 (IIA) of the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Other alkaline metals include beryllium, magnesium, calcium, barium, and radium. Strontium occupies a middle position in the family. Chemically, it is more active than calcium or magnesium, above it in the periodic table. But it is less active than barium, below it in Group 2.

Chemical Properties

Strontium is so active it must be stored under kerosene or mineral oil. In this way, the metal does not come into contact with air. In a finely divided or powdered form, strontium catches fire spontaneously and bums vigorously. Strontium is active enough to combine even with hydrogen and nitrogen when heated. The compounds formed are strontium hydride (SrH2) and strontium nitride (Sr3N2). Strontium also reacts with cold water and with acids to release hydrogen gas:

Occurrence In Nature

Strontium is a relatively abundant element in the Earth's crust. It ranks about 15th among the elements found in the Earth. That makes it about as abundant as fluorine and its alkaline earth partner, barium.

The most common minerals containing strontium are celestine and strontianite. Celestine contains primarily strontium sulfate (SrSO4), while strontianite contains mostly strontium carbonate (SrCO3). Important world sources of strontium are Mexico, Spain, Turkey, and Iran. A small amount of strontium is also obtained from mines in California and Texas.

Physical Properties

Strontium is a silvery-white, shiny metal. When exposed to air, it combines with oxygen to form a thin film of strontium oxide (SrO). The film gives the metal a yellowish color.

Strontium has a melting point of about 757°C (1,395°F) and a boiling point of 1,366°C (2,491°F). Its density is 2.6 grams per cubic centimeter.

Isotopes

Four isotopes of strontium occur in nature. They are strontium-84, strontium-86, strontium-87, and strontium-88. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.