Hormonal contraceptives (the pill, the patch, and the vaginal ring) all contain a small amount of man-made estrogen and progestin hormones. These hormones work to inhibit the body's natural cyclical hormones to prevent pregnancy. Pregnancy is prevented by a combination of factors.
Definition of STRONTIUM 90. : a heavy radioactive isotope of strontium of mass number 90 that has a half-life of 29 years, that is present in nuclear waste and fallout, and that is hazardous because like calcium it can be assimilated in biological processes and deposited in the bones of human beings and animals.See strontium 90 defined for kids. a heavy radioactive isotope of strontium having the mass number 90 that is present in the fallout from nuclear explosions and is hazardous because like calcium it can be assimilated in biological processes and deposited in the bones of human beings and animalsâcalled also radiostrontium.
Isotopes: 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.