The Representative Elements: Group 5A Through 8A Copyright © Houghton Mifflin Company. All rights reserved. 19a–2 Figure 19.1: Pyramidal shape of the Group 5A MX3 molecules Copyright © Houghton Mifflin Company. All rights reserved. 19a–3 Figure 19.2: Trigonal bipyramidal shape of the MX5 molecules Copyright © Houghton Mifflin Company. All rights reserved. 19a–4 Figure 19.3: Octahedral PF6- Copyright © Houghton Mifflin Company. All rights reserved. 19a–5 Figure 19.4: Structures of the tetrahedral MX4+ and the octahedral MX6- ions Copyright © Houghton Mifflin Company. All rights reserved. 19a–6 Figure 19.5: Inert atmosphere box Source: Corbis Copyright © Houghton Mifflin Company. All rights reserved. 19a–7 Properties of Nitrogen Atomic Number Density (g/L) Melting Point (oC) Boiling Point (oC) Atomic Radius (pm) Ionic Radius, N-3 (pm) Electronegativity Copyright © Houghton Mifflin Company. All rights reserved. 7 1.25 -210 -196 74 171 3.0 19a–8 How Air Bags Work In an accident, sensors initiate the reaction with a spark 2NaN3(s) => 2Na(s) + 3N2(g) reactive sodium destroyed by 10Na(s) + 2KNO3(s) => K2O(s) + 5Na2O(s) + N2(s) heat converts hazardous products into glass K2O(s) + Na2O(s) + SiO2(s)heat => glass Copyright © Houghton Mifflin Company. All rights reserved. 19a–9 Ostwald Process: Nitric Acid 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(aq) + NO(g) Copyright © Houghton Mifflin Company. All rights reserved. Figure 19.6: Schematic diagram of the Haber process for the manufacture of ammonia. Copyright © Houghton Mifflin Company. All rights reserved. 19a–11 Figure 19.7: Nitrogen cycle Copyright © Houghton Mifflin Company. All rights reserved. 19a–12 Nitrogen Cycle Copyright © Houghton Mifflin Company. All rights reserved. 19a–13 Nodules on the roots of pea plants contain nitrogen-fixing bacteria. Source: Photo Researchers, Inc. Copyright © Houghton Mifflin Company. All rights reserved. 19a–14 Figure 19.8: Molecular structure of hydrazine (N2H4) Copyright © Houghton Mifflin Company. All rights reserved. 19a–15 Blowing agents--such as hydrazine, which forms nitrogen gas on decomposition--are used to produce porous plastics like these polystyrene products. Copyright © Houghton Mifflin Company. All rights reserved. 19a–16 Copyright © Houghton Mifflin Company. All rights reserved. 19a–17 Copper penny reacts with nitric acid to produce NO gas, which is immediately oxidized in air to give reddish brown NO2-. Source: Fundamental Photographs Copyright © Houghton Mifflin Company. All rights reserved. 19a–18 Figure 19.9: Molecular orbital energy-level diagram for nitric oxide (NO). Copyright © Houghton Mifflin Company. All rights reserved. 19a–19 Copyright © Houghton Mifflin Company. All rights reserved. 19a–20 Kissing bug Source: Photo Researchers, Inc. Copyright © Houghton Mifflin Company. All rights reserved. 19a–21 Three-dimensional complex nitrohphorin-1 Source: Department of Biochemistry, University of Arizona, Tuscon Copyright © Houghton Mifflin Company. All rights reserved. 19a–22 Properties of Phosphorus Atomic Number Density (g/L) Melting Point (oC) Boiling Point (oC) Atomic Radius (pm) Ionic Radius, P-1 (pm) Electronegativity Copyright © Houghton Mifflin Company. All rights reserved. 15 1.82 44 280 110 212 2.1 19a–23 Phosphate Fertilizers Copyright © Houghton Mifflin Company. All rights reserved. 19a–24 Copyright © Houghton Mifflin Company. All rights reserved. 19a–25 Isolation of P 2Ca3(PO4)2 +6SiO2 +10C (1500°C) 6CaSiO3 + 10CO + P4 The reaction may proceed via "phosphorus pentoxide", P4O10 2Ca3(PO4)2 + 6SiO2 P4O10 + 10C Copyright © Houghton Mifflin Company. All rights reserved. 6CaSiO3 + P4O10 10CO + P4 19a–26 磷 •used in the manufacture of safety matches, pyrotechnics, incendiary shells, smoke bombs, tracer bullets, etc. •Fertilisers(肥料) •phosphates are used in the production of special glasses, such as those used for sodium lamps •bone-ash, calcium phosphate, is used to produce fine chinaware and to produce monocalcium phosphate used in baking powder •important in the production of steels, phosphor bronze, and many other products •Na3PO4 is important as a cleaning agent, as a water softener, and for preventing boiler scale and corrosion of pipes and boiler tubes •pesticides (殺蟲劑) Copyright © Houghton Mifflin Company. All rights reserved. 19a–27 磷循環 Copyright © Houghton Mifflin Company. All rights reserved. 19a–28 FeAsS (700°C) FeS + As(g) As(s) 砷 •bronzing •pyrotechnics •doping agent in solid-state devices such as transistors •the arsenide is used as a laser material to convert electricity directly into coherent light Copyright © Houghton Mifflin Company. All rights reserved. 19a–29 Sulfur Isotopes Copyright © Houghton Mifflin Company. All rights reserved. 19a–30 Frasch Process for Extracting Sulfur Copyright © Houghton Mifflin Company. All rights reserved. 19a–31 Sulfuric Acid • concentrated (large amount of solute) – strong acid – dehydrating agent – oxidizing agent industrial production • by-product of roasting of sulfide ores or from scrubbers in fossil fuel burning plants • produced from elemental sulfur by burning in air using catalysis (contact process) Copyright © Houghton Mifflin Company. All rights reserved. Properties of Sulfuric Acid • concentrated (large amount of solute) – strong acid – dehydrating agent – oxidizing agent Copyright © Houghton Mifflin Company. All rights reserved. Sulfuric Acid Production S8(s) + 8O2(g) => 8SO2(g) 2 SO2(g) + O2(g) => 2 SO3(g) SO3(g) + H2O(l) => H2SO4(aq) Copyright © Houghton Mifflin Company. All rights reserved. Preparation of Se Cu2Se + Na2CO3 + 2O2 2CuO + Na2SeO3 + CO2 The selenite Na2SeO3 is acidified with sulphuric acid. Any tellurites precipitateout leaving selenous acid, H2SeO3, in solution. Selenium is liberated from selenous acid by SO2 H2SeO3 + 2SO2 + H2O Copyright © Houghton Mifflin Company. All rights reserved. Se + 2H2SO4 19a–35 Downs Cell Copyright © Houghton Mifflin Company. All rights reserved. 19a–36 Chlor-Alkali Process Copyright © Houghton Mifflin Company. All rights reserved. 19a–37 Production of Phosphorus in Electric Furnace Copyright © Houghton Mifflin Company. All rights reserved. 19a–38 Phosphorus Allotropes Copyright © Houghton Mifflin Company. All rights reserved. 19a–39 Industrial Preparation by Electrolysis • Na+ + Cl- + H2O Na+ + 1/2Cl2 + 1/2H2 + OH- Laboratory Preparation MnO2 + 4HCl MnCl2 + Cl2 + 2H2O Copyright © Houghton Mifflin Company. All rights reserved. 19a–40 Copyright © Houghton Mifflin Company. All rights reserved. 19a–41 Properties of Bromine Atomic Number Density (g/L) Melting Point (oC) Boiling Point (oC) Atomic Radius (pm) Ionic Radius, Br-1 (pm) Electronegativity Copyright © Houghton Mifflin Company. All rights reserved. 35 3.12 -7 59 114 196 2.7 19a–42 Bromine and Iodine Cl 2 (g) + 2 Br - (aq) Br 2 ( ) + 2 Cl - - Cl 2 (g) + 2 I (aq) I 2 (aq) + 2 Cl - E° = +0.293 V E° = +0.823 V Laboratory Preparation: NaBr (s) + H2SO4 (l) HBr (g) + NaHSO4 (s) 2HBr (g) + H2SO4 (l) Br2 (g) + SO2 (g) + 2H2O (l) Copyright © Houghton Mifflin Company. All rights reserved. 19a–43 Bromine Use •fumigants •flameproofing agents •water purification compounds •dyes •medicines • (AgBr) used for photography •pesticides •water purification •used to make plastics flame retardant Copyright © Houghton Mifflin Company. All rights reserved. 19a–44 Properties of Iodine Atomic Number Density (g/L) Melting Point (oC) Boiling Point (oC) Atomic Radius (pm) Ionic Radius, I-1 (pm) Electronegativity 53 4.92 114 184 133 220 2.2 •iodide, and thyroxin which contains iodine, are used internally in medicine. A solution of KI and iodine in alcohol is used as a disinfectant for external wounds. •silver iodide is used in photography •nutrient •added to table salt for nutrition {stops goitres, (Derbyshire neck)} •deep blue colour in a starch solution is a sign of the free element Copyright © Houghton Mifflin Company. All rights reserved. 19a–45 Hydrogen Halides HX Copyright © Houghton Mifflin Company. All rights reserved. 19a–46 Copyright © Houghton Mifflin Company. All rights reserved. 19a–47 bond enthalpy of HX (kJ mol-1) electron affinity of X (kJ mol-1) hydration enthalpy of X(kJ mol-1) sum of these (kJ mol-1) HF +562 -328 -506 -272 HCl +431 -349 -364 -282 HBr +366 -324 -335 -293 HI +299 -295 -293 -289 Copyright © Houghton Mifflin Company. All rights reserved. 19a–48