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Chapter 22 Chemistry of the Nonmetals

Chemistry: A Molecular Approach , 1 st Ed. Nivaldo Tro. Chapter 22 Chemistry of the Nonmetals. Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA. 2008, Prentice Hall. Nanotubes. nanotubes – long, thin, hollow cylinders of atoms

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Chapter 22 Chemistry of the Nonmetals

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  1. Chemistry: A Molecular Approach, 1st Ed.Nivaldo Tro Chapter 22Chemistry of the Nonmetals Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA 2008, Prentice Hall

  2. Nanotubes • nanotubes – long, thin, hollow cylinders of atoms • carbon nanotube = sp2 C in fused hexagonal rings • electrical conductors • boron-nitride nanotubes = rings of alternating B and N atoms • isoelectronic with C • similar size to C • average electronegativity of B & N about the same as C • electrical insulators Tro, Chemistry: A Molecular Approach

  3. Insulated Nanowire Tro, Chemistry: A Molecular Approach

  4. Properties of BN and C Tro, Chemistry: A Molecular Approach

  5. Main Group Nonmetals Tro, Chemistry: A Molecular Approach

  6. Atomic Radius and Bonding • atomic radius decreases across the period • electronegativity, ionization energy increase across the period • nonmetals on right of p block form anions in ionic compounds • often reduced in chemical reactions • making them oxidizing agents • nonmetals on left of p block can form cations and electron-deficient species in covalent bonding • nonmetals near the center of the p block tend to use covalent bonding to complete their octets • bonding tendency changes across the period for nonmetals from cation and covalent; to just covalent; to anion and covalent Tro, Chemistry: A Molecular Approach

  7. Silicates • the most abundant elements of the Earth’s crust are O and Si • silicates are covalent atomic solids of Si and O • and minor amounts of other elements • found in rocks, soils, and clays • silicates have variable structures – leading to the variety of properties found in rocks, clays, and soils Tro, Chemistry: A Molecular Approach

  8. Bonding in Silicates • each Si forms a single covalent bond to 4 O • sp3 hybridization • tetrahedral shape • Si-O bond length is too long to form Si=O • to complete its octet, each O forms a single covalent bond to another Si • the result is a covalent network solid Tro, Chemistry: A Molecular Approach

  9. Quartz • a 3-dimensional covalent network of SiO4 tetrahedrons • generally called silica • formula unit is SiO2 • when heated above 1500C and cooled quickly, get amorphous silica which we call glass Tro, Chemistry: A Molecular Approach

  10. Aluminosilicates • Al substitutes for Si in some of the lattice sites • SiO2 becomes AlO2− • the negative charge is countered by the inclusion of a cation • Albite = ¼ of Si replaced by Al; Na(AlO2)(SiO2)3 • Anorthite = ½ of Si replaced by Al; Ca(AlO2)2(SiO2)2 Tro, Chemistry: A Molecular Approach

  11. Silicates Made of Individual Units • O of SiO4 picks up electrons from metal to form SiO44− • if the SiO44− are individual units neutralized by cations, it forms an orthosilicate • willemite = Zn2SiO4 • when two SiO4 units share an O, they form structures called pyrosilicateswith the anion formula Si2O76− • hardystonite =Ca2ZnSi2O7 Tro, Chemistry: A Molecular Approach

  12. Single Chain Silicates • if the SiO44− units link as long chains with shared O, the structure is called a pyroxene • formula unit SiO32- • chains held together by ionic bonding to metal cations between the chains • diopside = CaMg(SiO3)2 where Ca and Mg occupy lattice points between the chains Tro, Chemistry: A Molecular Approach

  13. Double Chain Silicates • some silicates have 2 chains bonded together at ½ the tetrahedra – these are called amphiboles • often results in fibrous minerals • asbestos • tremolite asbestos = Ca2(OH)2Mg5(Si4O11)2 Tro, Chemistry: A Molecular Approach

  14. Sheet Silicates • when 3 O of each tetrahedron are shared, the result is a sheet structure called a phyllosilicate • formula unit = Si2O52− • sheets are ionically bonded to metal cations that lie between the sheets • talc and mica Tro, Chemistry: A Molecular Approach

  15. Mica: a Phyllosilicate Tro, Chemistry: A Molecular Approach

  16. Silicate Structures Tro, Chemistry: A Molecular Approach

  17. Boron • metalloid • at least 5 allotropes, whose structures are icosahedrons • each allotrope connects the icosahedra in different ways • less than 0.001% in Earth’s crust, but found concentrated in certain areas • almost always found in compounds with O • borax = Na2[B4O5(OH)4]8H2O • kernite = Na2[B4O5(OH)4]3H2O • colemanite = Ca2B6O115H2O • used in glass manufacturing – borosilicate glass = Pyrex • used in control rods of nuclear reactors Tro, Chemistry: A Molecular Approach

  18. Boron Trihalides • BX3 • sp2 B • trigonal planar, 120 bond angles • forms single bonds that are shorter and stronger than sp3 C • some overlap of empty p on B with full p on halogen • strong Lewis Acids Tro, Chemistry: A Molecular Approach

  19. Boron-Oxygen Compounds • form structures with trigonal BO3 units • in B2O3, six units are linked in a flat hexagonal B6O6 ring • melts at 450C • melt dissolves many metal oxides and silicon oxides to form glasses of different compositions Tro, Chemistry: A Molecular Approach

  20. Boranescloso-Boranes • compounds of B and H • used as reagent in hydrogenation of C=C • closo-Boranes have formula BnHn2− and form closed polyhedra with a BH unit at each vertex Tro, Chemistry: A Molecular Approach

  21. Boranesnido-Boranes and arachno-Boranes • nido-Boranes have formula BnHn+4 consisting of cage B missing one corner • arachno-Boranes have formula BnHn+6 consisting of cage B missing two or three corners Tro, Chemistry: A Molecular Approach

  22. Carbon • exhibits the most versatile bonding of all the elements • diamond structure consists of tetrahedral sp3 carbons in a 3-dimensional array • graphite structures consist of trigonal planar sp2 carbons in a 2-dimensional array • sheets attracted by weak dispersion forces • fullerenes consist of 5 and 6 member carbon rings fused into icosahedral spheres of at least 60 C Tro, Chemistry: A Molecular Approach

  23. Crystalline Allotropes of Carbon

  24. Allotropes of Carbon - Diamond Inert to Common Acids Inert to Common Bases Negative Electron Affinity Transparent Hardest Best Thermal Conductor Least Compressible Stiffest Tro, Chemistry: A Molecular Approach

  25. Allotropes of Carbon - Graphite Soft and Greasy Feeling Solid Lubricant Pencil “Lead” Conducts Electricity Reacts with Acids and Oxidizing Agents Tro, Chemistry: A Molecular Approach

  26. Noncrystalline Forms of Carbon • coal is a mixture of hydrocarbons and carbon-rich particles • the product of carbonation of ancient plant material • carbonation removes H and O from organic compounds in the form of volatile hydrocarbons and water • anthracite coal has highest C content • bituminous coal has high C, but high S • heating coal in the absence of air forms coke • carbon and ash • heating wood in the absence of air forms charcoal • activated carbon is charcoal used to adsorb other molecules • soot is composed of hydrocarbons from incomplete combustion • carbon black is finely divided form of carbon that is a component of soot • used as rubber strengthener Tro, Chemistry: A Molecular Approach

  27. Allotropes of Carbon - Buckminsterfullerene Sublimes between 800°C Insoluble in water Soluble in toluene Stable in air Requires temps > 1000°C to decompose High electronegativity Reacts with alkali metals Behavior more aliphatic than aromatic Tro, Chemistry: A Molecular Approach

  28. Nanotubes • long hollow tubes constructed of fused C6 rings • electrical conductors • can incorporate metals and other small molecules and elements • used to stabilize unstable molecules • single-walled nanotubes (SWNT) have one layer of fused rings • multi-walled nanotubes (MWNT) have concentric layers of fused rings Tro, Chemistry: A Molecular Approach

  29. Nanotubes Tro, Chemistry: A Molecular Approach

  30. Nanocars Tro, Chemistry: A Molecular Approach

  31. Carbides • carbides are binary compounds of C with a less electronegative element • ionic carbides are compounds of metals with C • generally alkali or alkali earth metals • often dicarbide ion, C22− (aka acetylide ion) • react with water to form acetylene, C2H2 • covalent carbides are compounds of C with a low-electronegativity nonmetal or metalloid • silicon carbide, SiC (aka carborundum) • very hard • metallic carbides are metals in which C sits in holes in the metal lattice • hardens and strengthens the metal without affecting electrical conductivity • steel and tungsten carbide Tro, Chemistry: A Molecular Approach

  32. Calcium Carbide Tro, Chemistry: A Molecular Approach

  33. CementiteFe3C regions found in steel Tro, Chemistry: A Molecular Approach

  34. Carbon Oxides • CO2 • 0.04% in atmosphere • increased by 25% over the past century • high solubility in water • due to reaction with water to form HCO3− ions • triple point −57C and 5.1 atm • liquid CO2 doesn’t exist at atmospheric pressure • solid CO2 = dry ice • CO • colorless, odorless, tasteless gas • relatively reactive • 2 CO + O2  2 CO2 • burns with a blue flame • reduces many nonmetals • CO + Cl2  COCl2 (phosgene) • CO + S  COS (fungicide) Tro, Chemistry: A Molecular Approach

  35. Carbonates • solubility of CO2 in H2O due to carbonate formation • CO2 + H2O  H2CO3 • H2CO3 + H2O  H3O+ + HCO3− • HCO3−+ H2O  H3O+ + CO32− • washing soda = Na2CO310H2O • doesn’t decompose on heating • all carbonate solutions are basic in water • due to CO32−+ H2O  OH− + HCO32− • baking soda = NaHCO3 • decomposes on heating to Na2CO3, H2O and CO2 Tro, Chemistry: A Molecular Approach

  36. Elemental Nitrogen • N2 • 78% of atmosphere • purified by distillation of liquid air, or filtering air through zeolites • very stable, very unreactive • NN Tro, Chemistry: A Molecular Approach

  37. Elemental Phosphorus • P • white phosphorus • white, soft, waxy solid that is flammable and toxic • stored under water to prevent spontaneous combustion • 2 Ca3(PO4)2 (apatite) + 6 SiO2 + 10 C  P4(g, wh) + 6 CaSiO3 + 10 CO • tetrahedron with small angles 60 • red phosphorus • formed by heating white P to about 300C in absence of air • amorphous • mostly linked tetrahedra • not as reactive or toxic as white P • used in match heads • black phosphorus • formed by heating white P under pressure • most thermodynamically stable form, therefore least reactive • layered structure similar to graphite Tro, Chemistry: A Molecular Approach

  38. White Phosphorus Red Phosphorus Phosphorus Tro, Chemistry: A Molecular Approach

  39. Hydrides of Nitrogen • ammonia, NH3 • pungent gas • basic NH3 + H2O  NH4+ + OH− • reacts with acids to make NH4+ salts • used as chemical fertilizers • made by fixing N from N2 using the Haber-Bosch process • hydrazine, N2H4 • colorless liquid • basic N2H4 + H2O  N2H5+ + OH− • powerful reducing agent • hydrogen azide, HN3 • acidic HN3 + H2O  H3O+ + N3− • thermodynamically unstable and decomposes explosively to its elements Tro, Chemistry: A Molecular Approach

  40. Hydrazine Tro, Chemistry: A Molecular Approach

  41. Oxides of Nitrogen • formed by reaction of N2 or NOx with O2 • all unstable and will eventually decompose into N2 and O2 • NO = nitrogen monoxide = nitric oxide • important in living systems • free radical • NO2 = nitrogen dioxide • 2 NO2 N2O4 • red-brown gas • free radical • N2O = dinitrogen monoxide = nitrous oxide • laughing gas • made by heating ammonium nitrate NH4NO3  N2O + H2O • oxidizing agent Mg + N2O  N2 + MgO • decomposes on heating 2 N2O  2 N2 + O2 • pressurize food dispensers Tro, Chemistry: A Molecular Approach

  42. Tro, Chemistry: A Molecular Approach

  43. Nitric Acid • HNO3 = nitric acid • produced by the Ostwald Process 4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g) 2 NO(g) + O2(g)  2 NO2(g) 3 NO2(g) + H2O(l)  2 HNO3(l) + NO(g) • strong acid • strong oxidizing agent • concentrated = 70% by mass = 16 M • some HNO3 in bottle reacts with H2O to form NO2 • main use to produce fertilizers and explosives NH3(g) + HNO3(aq)  NH4NO3(aq) Tro, Chemistry: A Molecular Approach

  44. Nitrates and Nitrites • NO3− = nitrate • ANFO = ammonium nitrate fuel oil • used as explosive in Oklahoma City • ammonium nitrate can decompose explosively • and other nitrates 2 NH4NO3 2 N2 + O2 + 4 H2O • metal nitrates used to give colors to fireworks • very soluble in water • oxidizing agent • NO2− = nitrite • NaNO2 used as food preservative in processed meats • kills botulism bacteria • keeps meat from browning when exposed to air • can form nitrosamines which may increase risk of colon cancer?? Tro, Chemistry: A Molecular Approach

  45. Phosphine • PH3 • colorless, poisonous gas that smells like rotting fish • formed by reacting metal phosphides with water Ca3P2(s) + 6 H2O(l) 2 PH3(g) + 3 Ca(OH)2(aq) • also by reaction of wh P with H2O in basic solution 2 P4(s) + 9 H2O(l) + 3 OH−(aq) 5 PH3(g) + 3 H2PO4−(aq) • decomposes on heating to elements 4 PH3(g) P4(s) + 6 H2(g) • reacts with acids to form PH4+ ion • does not form basic solutions Tro, Chemistry: A Molecular Approach

  46. Phosphorus Halides • P4 can react directly with halogens to form PX3 and PX5 compounds • PX3 can react with water to form H3PO3 • PX5 can react with water to form H3PO4 PCl3(l) + 3 H2O(l) H3PO3(aq) + 3 HCl(aq) • PCl3 reacts with O2 to form POCl3(l) • phosphorus oxychloride • other oxyhalides made by substitution on POCl3 • phosphous halide and oxyhalides are key starting materials in the production of many P compounds • fertilizers, pesticides, oil-additives, fire-retardants, surfactants Tro, Chemistry: A Molecular Approach

  47. Phosphorus Oxides • P4 reacts with O2 to make P4O6(s) or P4O10(s) • get P4O10 with excess O2 Tro, Chemistry: A Molecular Approach

  48. Phosphoric Acid and Phosphates • H3PO4 = phosphoric acid • white solid that melts at 42C • concentrated = 85% by mass = 14.7 M • produced by reacting P4O10 with water or the reaction of Ca3(PO4)2 with sulfuric acid P4O10(s) + 6 H2O(l) 4 H3PO4(aq) Ca3(PO4)2(s) + 3 H2SO4(l) 3 CaSO4(s) + 2 H3PO4(qa) • used in rust removal, fertilizers, detergent additives and food preservative • sodium pyrophosphate = Na4P2O7 • sodium tripolyphosphate = Na5P3O10 Tro, Chemistry: A Molecular Approach

  49. Use of Phosphates in Food Tro, Chemistry: A Molecular Approach

  50. Oxygen • 2s22p4 • 6 valence electrons • stronger oxidizing agent than other 6A elements • used by living system to acquire energy • second highest electronegativity (3.5) • very high abundance in crust, and highest abundance of any element on Earth • found in most common compounds Tro, Chemistry: A Molecular Approach

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