High Quality Content by WIKIPEDIA articles! Strontium (pronounced /?str?n?i?m/ STRON-shee-?m, /?str?nti?m/ STRON-tee-?m, or /?str?n??m/ STRON-sh?m) is a chemical element with the symbol Sr and the atomic number 38 An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically однюо The metal turns yellow when exposed to air It occurs naturally in the minerals celestine and strontianite The 90Sr isotope is present in radioactive fallout and has a half-life of 28 90 years Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was first discovered.  Eyesigh2010 г Мягкая обложка, 64 стр ISBN 6130368755.