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Chapter_13_Notes - Group 14 C Si Ge Sn Pb C Si are...

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1 Group 14 Shriver, Chapter 13 C, Si, Ge, Sn, Pb C, Si are non-metals Ge is a metalloid Sn, Pb are metals Chemical hardness decreases down the group (C, Si: oxophilic, fluorophilic) Major oxidation state +4 except for lead: Pb(II) Pb forms most stable complexes with soft anions: S, I Metallic properties increase down the group Carbon Most abundant form in the atmosphere: CO 2 , and in the Earth’s crust: MCO 3 Elemental forms known since prehistory: charcoal, soot (used in inks), diamond, graphite Name coined by Lavoisier from carbo (Latin, charcoal) Naturally occurring forms of the element (allotropes) are graphite (Greek graphein , to write) and diamond (from Greek diaphanes (transparent) with adamas (indomitable)) First ‘lead’ pencils manufactured 1564 contained graphite (they still do) New allotrope discovered 1985, in molecular beam experiments: C 60 , C 70 , C 76 , C 84 named buckminsterfullerenes, for the architect Richard Buckminster Fuller, who designed geodesic domes have since been found to occur naturally in candle soot, lightning discharges now called fullerenes, or buckyballs C 60 structure is a truncated icosahedron, 20 hexagons and 12 pentagons, approx. 1 nm in diameter elongated versions: carbon nanotubes, concentric cylinder of hexagons, with buckyball ends, of interest in hydrogen storage Major uses of C are: as a fuel (coal), as a reducing agent for metal ores (coke), diamond cutting tools as a lubricant (graphite), also in pencils, fuel cell anodes Important uses of C in science: 13 C NMR, 14 C radio-carbon dating Silicon 26% of the earth’s crust by weight, most abundant element after O found in sand, quartz, clay, etc name from the Latin silicis (flint) for Paleolithic tools (from silica and silicates) element first isolated in 1823 by reducing K 2 SiF 6 with K now made by SiO 2 + 2 C + heat Si + 2 CO a semiconductor, used in microelectronics industry one of the purest materials made on an industrial scale, impurities ca. 10 -10 routine
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2 Germanium eka-silicon predicted by Mendeleev discovered in 1886 by Winkler, in rare mineral argyrodite Ag 8 GeS 6 named in honor of Germany low abundance, like Ga major source today: recovery of GeO 2 from flue dust of smelters processing Zn ores a semiconductor, like Si, but with a smaller bandgap used in IR transparent windows, detectors Tin Occurs naturally as the mineral cassiterite (SnO 2 ) Elemental form obtained by reduction with C Latin stannum , known to the ancients bronze is10-15% tin alloyed with copper used to make cups, cutlery, buttons, kerosene containers (Arctic expeditions)
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Chapter_13_Notes - Group 14 C Si Ge Sn Pb C Si are...

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