OXYGEN -named after Greek “oxy genes” meaning acid forming -Discovered by Joseph Priestley 1774 in Wiltshire, England and by C.W. Scheele in Uppsala, Sweden - Priestley focused sunlight on mercuric oxide and realized the gas made it easier to breath and made burning candles brighter -First appeared on Earth 2 billion years ago as a product of blue- green algae photosynthesis

OXYGEN colorless, odorless gas - makes up 21% of the atmosphere Allotropes include O 2 and O 3 Melting point is ˚C and boiling point is ˚C most abundant isotope is 16 O Relative atomic mass is amu and atomic number is 8 Common oxidation states are -1 and -2 Density is g cm -3 Very reactive 6 valence electrons

OXYGEN Commerically used in steel industry to cut metals and used to clear sewage Manufacture of nitric oxide, hydrogen peroxide, anti-freeze, polyester, PVC Used during respiration Found in: Plastics atmosphere as O 3 (ozone) and CO 2 Water, rocks, soils

SULFUR Name derived from Sanskrit “sulvere” or Latin “sulfurium” Ancient history: Mentioned in Bible ancient Greeks used as fumigant Mined near Mt Etna (Sicily) and used to bleach cloth or preserve wine Thought to be component of all metals Discovered by Lavoisier, Guy-Lussac, Davy, Louis-Josef and Thenard 1808/1809

SULFUR Atomic number 16 and relative atomic mass amu Melting point °C and boiling point °C Density is 2.07 g cm -3 Most abundant isotope is 32 S Solid at room temperature Allotropes appear as yellow dust and crystals (S 2 and S 3 ) Common oxidation states are 6, 4, 2, -2 Smells like rotten eggs 6 valence electrons Non-reactive

SULFUR Used for vulcanization of rubber, detecting gas leaks, bleaching of paper and preserving food Manufacture pesticides, black gunpowder, sulfuric acid, detergents, cement and plaster Essential for life: Plants uptake as sulfate Amino acids Can be toxic: Hydrogen sulfide causes respiratory arrest Sulfur dioxide causes acid rain Can be found in: Fertilizer Medicine Fireworks and matches volcanoes