Matter & Energy


Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Strontium

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Strontium, symbol Sr, chemically reactive, malleable, ductile metallic element. In group 2 (or IIa) of the periodic table, strontium is one of the alkaline earth metals. The atomic number of strontium is 38.

Metallic strontium was first isolated by the British chemist Sir Humphry Davy in 1808; the oxide had been known as early as 1790. Strontium has a silvery color when freshly cut. It oxidizes readily upon exposure to air, and reacts with water to produce strontium hydroxide and hydrogen gas. Like the other alkaline earth metals, it is prepared by transforming the carbonate or sulfate into the chloride, which, upon electrolysis, yields the metal. Strontium melts at about 769° C (about 1416° F), boils at about 1384° C (about 2523° F), and has a specific gravity of 2.6. The atomic weight of strontium is 87.62.

Strontium is never found in the elemental state, occurring chiefly as strontianite and celestite. Strontium ranks about 15th among the elements in natural abundance in the earth's crust and is widely distributed in small quantities. The greatest amounts are mined in Mexico, England, and Scotland. Because it emits a brilliant red color when burned in air, strontium is used in the manufacture of fireworks and railroad flares. Strontia (strontium oxide) is used in recovering sugar from beet-sugar molasses. A radioactive isotope of the element, strontium-85, is used in the detection of bone cancer. Strontium-90 is a dangerous radioactive isotope found in the fallout that results from the detonation of some nuclear weapons.
Strontium, symbol Sr, chemically reactive, malleable, ductile metallic element. In group 2 (or IIa) of the periodic table, strontium is one of the alkaline earth metals. The atomic number of strontium is 38.

Metallic strontium was first isolated by the British chemist Sir Humphry Davy in 1808; the oxide had been known as early as 1790. Strontium has a silvery color when freshly cut. It oxidizes readily upon exposure to air, and reacts with water to produce strontium hydroxide and hydrogen gas. Like the other alkaline earth metals, it is prepared by transforming the carbonate or sulfate into the chloride, which, upon electrolysis, yields the metal. Strontium melts at about 769° C (about 1416° F), boils at about 1384° C (about 2523° F), and has a specific gravity of 2.6. The atomic weight of strontium is 87.62.

Strontium is never found in the elemental state, occurring chiefly as strontianite and celestite. Strontium ranks about 15th among the elements in natural abundance in the earth's crust and is widely distributed in small quantities. The greatest amounts are mined in Mexico, England, and Scotland. Because it emits a brilliant red color when burned in air, strontium is used in the manufacture of fireworks and railroad flares. Strontia (strontium oxide) is used in recovering sugar from beet-sugar molasses. A radioactive isotope of the element, strontium-85, is used in the detection of bone cancer. Strontium-90 is a dangerous radioactive isotope found in the fallout that results from the detonation of some nuclear weapons.