Q. Show Occurrence Extraction of group 16?
Oxygen is the most abundant of all elements on earth. Dry air contains 20.946% oxygen by volume in the free form. Oxygen forms about 46.6% by weight df the earth's crust including the oceans and the atmosphere. Most of this combined oxygen is in the form of silicates. oxides and water. Water is one of the most abundant compounds on earth, present not only in oceans which cover three fourths of the earth's surface but also in the atmosphere as vapour and in the subterranean aquifers. Living organisms also contain large amounts of water. Water contains 88.8% of oxygen by weight.
By contrast, the abundance of sulphur in the earth's crust is only 0.03-0.19. It is often found as the free element near volcanic regions in japan. Sicily , Mexico and Luisiana in USA. Combined sulphur exists primarily in sulphates and sulphides. Such as gypsum. Ca SO4,. 2H2O. barite, BaSO4,, and epsom salt. MgSO4, 7H2O. The sulphides include galena. PbS. zinc blende. ZnS. chalcopyrite CuFeS2,. Iron pyrite. FeS2 and cinnabar. Hg S. etc It also occurs in mineral springs as H2S. Along with C. H. 3. N and P, sulphur is one of the twenty-three odd elements essential for life. It is a constituent of substances such as eggs, wool, hair and also mustard, garlic, cabbage, etc. Selenium and tellurium also occur as sulphide ores. Polonium occurs naturally as a decay product in thorium and uranium minerals.