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Group 16 Elements By Zach Bindell, Val Chin, & Kevin Pugh Chalcogens ● ● ● ● Each element contains six valence electrons Each element forms 2- ions Located in the p block of the periodic table The term chalcogen was first used by the Wilhelm Blitz research group at the University of Hannover in Germany Chalcogens ● The term calcogen in greek is literally “copper former” but can be translated to “ore former” or, more commonly, “chalk former” ● The characteristics of chalcogens vary dramatically because the group crosses the line between metals and nonmetals ● The elements are mostly solids at room temperature, excluding oxygen, which is a gas Oxygen ● ● ● ● ● ● ● ● Discovered in 1774 by Joseph Priestly in Wiltshire England after he did experiments with HgO (mercuric oxide). He found out that by exposing the chemical to sunlight it liberated a gas that is now recognized as pure oxygen (O2). The name comes from the greek ‘oxy genes’ meaning ‘acid forming’. Oxygen is a diatomic element naturally found as a colorless, odorless gas. It is also highly flammable. It makes up 21% of the Earth’s atmosphere, 49% by mass of the Earth’s crust, and ⅔ of the human body. The oxygen content in the atmosphere is at the perfect concentration so organisms don’t die of asphyxiation or spontaneously combust. O16 is the most abundant isotope (99.762%) Used in the production of a wide variety of chemicals including nitric acid and hydrogen peroxide. Used most commonly in the steel industry for welding and cutting metal. 16 Sulfur ■ ■ ■ S General Characteristics ○ Assryian texts from 700-600B.C. state sulfur is a “product of the riverside” 32.065 ○ Sulfur deposits were found along the rivers. SULFUR ○ Discovered in Northern Iraq Physical Characteristics ○ Solid at room temperature ○ Nonmetal ○ Yellow brittle crystals ○ Density = 2.07g/cm3 ○ Melting Point = 115.21oC, Boiling Point = 444.62oC Unique Facts ○ Used for organic insecticides, preservatives for dried fruits, and fertilizers ○ Extracted from the Earth by Frasch processes. Selenium ● ● ● ● ● ● ● Discovered in 1817 by Jöns Jacob Berzelius after observing a red-brown sediment collected as a bi product of sulfuric acid. The name comes from ‘selene’ the Greek name for moon. Selenium is a metalloid naturally found in either a silvery metal or a red powder. It is an essential trace element in humans however in excess can act as a carcinogen. Most abundant isotopes: 80Se(49.6%), 78Se(23.7%), 76Se(9.4%). Used as an additive to glass to make it clear. Used in photocells, solar cells, and photocopiers because it is useful in converting light energy to electrical energy. 52 Tellurium ■ ■ ■ Te General Characteristics ○ Discovered by Franz Joseph Miller von Reichstein in Romania, 1783 127.60 TELLURIUM ○ Found in gold ores ○ He was intrigued by the metallic sheen in gold ore and discovered Tellurium Physical Characteristics ○ Solid at room temperature ○ Grey powder ○ Density = 6.232g/cm3 ○ Melting Point = 449.51oC, Boiling Point = 988oC Unique Facts ○ Used with copper and stainless steel to improve machinability ○ Very toxic metalloid ○ If workers mining Tellurium are exposed to tellurium, they get “tellurium breath” that smells like garlic breath. Polonium-Po ● Named for the country of Poland, where it was discovered ● A silvery grey radioactive semimetal which is a solid at room temperature ● Melting point: 254°C, 489°F ● Boiling point: 962°C, 1764°F ● Density: 9.32 g/cm3 ● Used as an alpha emitter ● Used as a source of heat in space equipment ● Very rare natural element ● Mendeleev predicted Po would exist because of a missing space on his periodic table ● In 1898 Marie Curie and husband Pierre extracted some Polonium from pitchblende (uranium oxide, U3O8)