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

Tro, Chemistry: A Molecular Approach2 Nanotubes nanotubes – long, thin, hollow cylinders of atoms carbon nanotube = sp 2 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 Approach3 Properties of BN and C

Tro, Chemistry: A Molecular Approach4 Main Group Nonmetals

Tro, Chemistry: A Molecular Approach5 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 Approach6 Insulated Nanowire

Tro, Chemistry: A Molecular Approach7 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 Approach8 Bonding in Silicates each Si forms a single covalent bond to 4 O sp 3 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 Approach9 Quartz a 3-dimensional covalent network of SiO 4 tetrahedrons generally called silica formula unit is SiO 2 when heated above 1500  C and cooled quickly, get amorphous silica which we call glass

Tro, Chemistry: A Molecular Approach10 Aluminosilicates Al substitutes for Si in some of the lattice sites SiO 2 becomes AlO 2 − the negative charge is countered by the inclusion of a cation Albite = ¼ of Si replaced by Al; Na(AlO 2 )(SiO 2 ) 3 Anorthite = ½ of Si replaced by Al; Ca(AlO 2 ) 2 (SiO 2 ) 2

Tro, Chemistry: A Molecular Approach11 Silicates Made of Individual Units O of SiO 4 picks up electrons from metal to form SiO 4 4− if the SiO 4 4− are individual units neutralized by cations, it forms an orthosilicate willemite = Zn 2 SiO 4 when two SiO 4 units share an O, they form structures called pyrosilicates with the anion formula Si 2 O 7 6− hardystonite =Ca 2 ZnSi 2 O 7

Tro, Chemistry: A Molecular Approach12 Single Chain Silicates if the SiO 4 4− units link as long chains with shared O, the structure is called a pyroxene formula unit SiO 3 2- chains held together by ionic bonding to metal cations between the chains diopside = CaMg(SiO 3 ) 2 where Ca and Mg occupy lattice points between the chains

Tro, Chemistry: A Molecular Approach13 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 = Ca 2 (OH) 2 Mg 5 (Si 4 O 11 ) 2

Tro, Chemistry: A Molecular Approach14 Sheet Silicates when 3 O of each tetrahedron are shared, the result is a sheet structure called a phyllosilicate formula unit = Si 2 O 5 2− sheets are ionically bonded to metal cations that lie between the sheets talc and mica

Tro, Chemistry: A Molecular Approach15 Mica: a Phyllosilicate

Tro, Chemistry: A Molecular Approach16 Silicate Structures

Tro, Chemistry: A Molecular Approach17 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 = Na 2 [B 4 O 5 (OH) 4 ]  8H 2 O  kernite = Na 2 [B 4 O 5 (OH) 4 ]  3H 2 O  colemanite = Ca 2 B 6 O 11  5H 2 O used in glass manufacturing – borosilicate glass = Pyrex used in control rods of nuclear reactors

Tro, Chemistry: A Molecular Approach18 Boron Trihalides BX 3 sp 2 B trigonal planar, 120  bond angles forms single bonds that are shorter and stronger than sp 3 C some overlap of empty p on B with full p on halogen strong Lewis Acids

Tro, Chemistry: A Molecular Approach19 Boron-Oxygen Compounds form structures with trigonal BO 3 units in B 2 O 3, six units are linked in a flat hexagonal B 6 O 6 ring melts at 450  C  melt dissolves many metal oxides and silicon oxides to form glasses of different compositions

Tro, Chemistry: A Molecular Approach20 Boranes closo-Boranes compounds of B and H used as reagent in hydrogenation of C=C closo-Boranes have formula B n H n 2− and form closed polyhedra with a BH unit at each vertex

Tro, Chemistry: A Molecular Approach21 Boranes nido-Boranes and arachno-Boranes nido-Boranes have formula B n H n+4 consisting of cage B missing one corner arachno-Boranes have formula B n H n+6 consisting of cage B missing two or three corners

Tro, Chemistry: A Molecular Approach22 Carbon exhibits the most versatile bonding of all the elements diamond structure consists of tetrahedral sp 3 carbons in a 3-dimensional array graphite structures consist of trigonal planar sp 2 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

23 Crystalline Allotropes of Carbon DiamondGraphiteBuckminster- fullerene, C 60 Colorclear-blueblack Density, g/cm Hardness, Mohs Scale100.5 Electrical Conductivity, (  cm) -1 ~ x ~ Thermal Conductivity, W/cmK23 20 (  ) Melting Point,  C ~3700~ sublimes Heat of Formation (kcal/mol) Refractive Index2.42─2.2 (600 nm) SourceKimberlite (S. Africa) Pegmatite (Sri Lanka) Shungite (Russia)

Tro, Chemistry: A Molecular Approach24 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 Approach25 Allotropes of Carbon - Graphite Soft and Greasy Feeling Solid Lubricant Pencil “Lead” Conducts Electricity Reacts with Acids and Oxidizing Agents

Tro, Chemistry: A Molecular Approach26 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 Approach27 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 Approach28 Nanotubes long hollow tubes constructed of fused C 6 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 Approach29 Nanotubes

Tro, Chemistry: A Molecular Approach30 Nanocars

Tro, Chemistry: A Molecular Approach31 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, C 2 2− (aka acetylide ion) react with water to form acetylene, C 2 H 2 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 Approach32 Calcium Carbide

Tro, Chemistry: A Molecular Approach33 Cementite Fe 3 C regions found in steel

Tro, Chemistry: A Molecular Approach34 Carbon Oxides CO % in atmosphere  increased by 25% over the past century high solubility in water  due to reaction with water to form HCO 3 − ions triple point −57  C and 5.1 atm  liquid CO 2 doesn’t exist at atmospheric pressure  solid CO 2 = dry ice CO colorless, odorless, tasteless gas relatively reactive  2 CO + O 2  2 CO 2 –burns with a blue flame  reduces many nonmetals –CO + Cl 2  COCl 2 (phosgene) –CO + S  COS (fungicide)

Tro, Chemistry: A Molecular Approach35 Carbonates solubility of CO 2 in H 2 O due to carbonate formation CO 2 + H 2 O  H 2 CO 3 H 2 CO 3 + H 2 O  H 3 O + + HCO 3 − HCO 3 − + H 2 O  H 3 O + + CO 3 2− washing soda = Na 2 CO 3  10H 2 O doesn’t decompose on heating all carbonate solutions are basic in water due to CO 3 2− + H 2 O  OH − + HCO 3 2− baking soda = NaHCO 3 decomposes on heating to Na 2 CO 3, H 2 O and CO 2

Tro, Chemistry: A Molecular Approach36 Elemental Nitrogen N 2 78% of atmosphere purified by distillation of liquid air, or filtering air through zeolites very stable, very unreactive NNNN

Tro, Chemistry: A Molecular Approach37 Elemental Phosphorus P white phosphorus  white, soft, waxy solid that is flammable and toxic  stored under water to prevent spontaneous combustion  2 Ca 3 (PO 4 ) 2 (apatite) + 6 SiO C  P 4 (g, wh) + 6 CaSiO 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 Approach38 Phosphorus White Phosphorus Red Phosphorus

Tro, Chemistry: A Molecular Approach39 Hydrides of Nitrogen ammonia, NH 3 pungent gas basic NH 3 + H 2 O  NH OH −  reacts with acids to make NH 4 + salts –used as chemical fertilizers made by fixing N from N 2 using the Haber-Bosch process hydrazine, N 2 H 4 colorless liquid basic N 2 H 4 + H 2 O  N 2 H OH − powerful reducing agent hydrogen azide, HN 3 acidic HN 3 + H 2 O  H 3 O + + N 3 − thermodynamically unstable and decomposes explosively to its elements

Tro, Chemistry: A Molecular Approach40 Hydrazine

Tro, Chemistry: A Molecular Approach41 Oxides of Nitrogen formed by reaction of N 2 or NO x with O 2 all unstable and will eventually decompose into N 2 and O 2 NO = nitrogen monoxide = nitric oxide important in living systems free radical NO 2 = nitrogen dioxide 2 NO 2  N 2 O 4 red-brown gas free radical N 2 O = dinitrogen monoxide = nitrous oxide laughing gas made by heating ammonium nitrate NH 4 NO 3  N 2 O + H 2 O oxidizing agent Mg + N 2 O  N 2 + MgO decomposes on heating 2 N 2 O  2 N 2 + O 2 pressurize food dispensers

Tro, Chemistry: A Molecular Approach42

Tro, Chemistry: A Molecular Approach43 Nitric Acid HNO 3 = nitric acid produced by the Ostwald Process 4 NH 3(g) + 5 O 2(g)  4 NO (g) + 6 H 2 O (g) 2 NO (g) + O 2(g)  2 NO 2(g) 3 NO 2(g) + H 2 O (l)  2 HNO 3(l) + NO (g) strong acid strong oxidizing agent concentrated = 70% by mass = 16 M  some HNO 3 in bottle reacts with H 2 O to form NO 2 main use to produce fertilizers and explosives NH 3(g) + HNO 3(aq)  NH 4 NO 3(aq)

Tro, Chemistry: A Molecular Approach44 Nitrates and Nitrites NO 3 − = nitrate ANFO = ammonium nitrate fuel oil  used as explosive in Oklahoma City ammonium nitrate can decompose explosively  and other nitrates 2 NH 4 NO 3  2 N 2 + O H 2 O metal nitrates used to give colors to fireworks very soluble in water oxidizing agent NO 2 − = nitrite NaNO 2 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 Approach45 Phosphine PH 3 colorless, poisonous gas that smells like rotting fish formed by reacting metal phosphides with water Ca 3 P 2(s) + 6 H 2 O (l)  2 PH 3(g) + 3 Ca(OH) 2(aq) also by reaction of wh P with H 2 O in basic solution 2 P 4(s) + 9 H 2 O (l) + 3 OH − (aq)  5 PH 3(g) + 3 H 2 PO 4 − (aq) decomposes on heating to elements 4 PH 3(g)  P 4(s) + 6 H 2(g) reacts with acids to form PH 4 + ion does not form basic solutions

Tro, Chemistry: A Molecular Approach46 Phosphorus Halides P 4 can react directly with halogens to form PX 3 and PX 5 compounds PX 3 can react with water to form H 3 PO 3 PX 5 can react with water to form H 3 PO 4 PCl 3(l) + 3 H 2 O (l)  H 3 PO 3(aq) + 3 HCl (aq) PCl 3 reacts with O 2 to form POCl 3(l) phosphorus oxychloride other oxyhalides made by substitution on POCl 3 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 Approach47 Phosphorus Oxides P 4 reacts with O 2 to make P 4 O 6(s) or P 4 O 10(s) get P 4 O 10 with excess O 2

Tro, Chemistry: A Molecular Approach48 Phosphoric Acid and Phosphates H 3 PO 4 = phosphoric acid white solid that melts at 42  C concentrated = 85% by mass = 14.7 M produced by reacting P 4 O 10 with water or the reaction of Ca 3 (PO 4 ) 2 with sulfuric acid P 4 O 10(s) + 6 H 2 O (l)  4 H 3 PO 4(aq) Ca 3 (PO 4 ) 2(s) + 3 H 2 SO 4(l)  3 CaSO 4(s) + 2 H 3 PO 4(qa) used in rust removal, fertilizers, detergent additives and food preservative  sodium pyrophosphate = Na 4 P 2 O 7  sodium tripolyphosphate = Na 5 P 3 O 10

Tro, Chemistry: A Molecular Approach49 Use of Phosphates in Food

Tro, Chemistry: A Molecular Approach50 Oxygen 2s 2 2p 4 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 Approach51 Elemental Oxygen O 2 nonpolar, colorless, odorless gas freezing point −183  C at which it becomes a pale blue liquid slightly soluble in water  0.04 g/L mainly produced by fractional distillation of air  also by the electrolysis of water can be synthesized by heating metal oxides, chlorates, or nitrates HgO (s)  Hg (l) + O 2(g) 2 NaNO 3(s)  2 NaNO 2(s) + O 2(g) 2 KClO 3(s)  2 KCl (s) + 3 O 2(g) used in high temperature combustion  blast furnace, oxyacetylene torch used to create artificial atmospheres  divers, high-altitude flight medical treatment  lung disease, hyperbaric O 2 to treat skin wounds

Tro, Chemistry: A Molecular Approach52 Oxides reacts with most other elements to form oxides both metals and nonmetals oxides containing O 2− with −2 oxidation state most stable for small ions with high charge oxides containing O 2 − with −½ oxidation state most stable for large ions with smaller charge

Tro, Chemistry: A Molecular Approach53 Ozone O 3 toxic, pungent, blue, diamagnetic gas denser than O 2 freezing point −112  C, where it becomes a blue liquid synthesized naturally from O 2 through the activation by ultraviolet light  mainly in the stratosphere  protecting the living Earth from harmful UV rays spontaneously decomposes into O 2 commercial use as a strong oxidizing agent and disinfectant formed in the troposphere by interaction of UV light and auto exhaust  oxidation damages skin, lungs, eyes, and cracks plastics and rubbers

Tro, Chemistry: A Molecular Approach54 Sulfur large atom and weaker oxidizer than oxygen often shows +2, +4, or +6 oxidation numbers in its compounds, as well as −2 composes 0.06% of Earth’s crust elemental sulfur found in a few natural deposits some on the surface below ground recovered by the Frasch Process superheated water pumped down into deposit, melting the sulfur and forcing it up the recovery pipe with the water also obtained from byproducts of several industrial processes

Tro, Chemistry: A Molecular Approach55 Natural Sulfur Deposit

Tro, Chemistry: A Molecular Approach56 Frasch Process

Tro, Chemistry: A Molecular Approach57 Allotropes of Sulfur several crystalline forms the most common naturally occurring allotrope has S 8 rings most others also ring structures of various sizes when heated to 112  C, S 8 melts to a yellow liquid with low viscosity when heated above 150  C, rings start breaking and a dark brown viscous liquid forms darkest at 180  C above 180  C the liquid becomes less viscous if the hot liquid is quenched in cold water, a plastic amorphous solid forms that becomes brittle and hard on cooling

Tro, Chemistry: A Molecular Approach58 sulfur at ~150  Csulfur at ~180  C

Tro, Chemistry: A Molecular Approach59 Amorphous Sulfur

Tro, Chemistry: A Molecular Approach60 Other Sources of Sulfur H 2 S (g) from oil and natural gas deposits toxic gas (death > 100 ppm), smells like rotten eggs bond angle only 92.5  nonpolar S-H bond weaker and longer than O-H bond oxidized to elemental S through the Claus Process 2 H 2 S (g) + 2 O 2(g)  2 SO 2(g) + 2 H 2 O (g) 4 H 2 S (g) + 2 SO 2(g)  6 S (s) + 4 H 2 O (g) FeS 2 (iron pyrite) roasted in absence of air forming FeS (s) and S 2(g) metal sulfides roasted in air to make SO 2(g), which is later reduced react with acids to make H 2 S most insoluble in water used as bactericide and stop dandruff in shampoo

Tro, Chemistry: A Molecular Approach61 Metal Sulfides

Tro, Chemistry: A Molecular Approach62 Sulfur Dioxide SO 2 colorless, dense, acrid gas that is toxic produced naturally by volcanic action and as a byproduct of industrial processes  including electrical generation by burning oil and coal, as well as metal extraction acidic SO 2(g) + H 2 O (l)  H 2 SO 3(aq) forms acid rain in the air 2 SO 2(g) + O 2(g) + 2 H 2 O (l)  2 H 2 SO 4(aq) removed from stack by scrubbing with limestone CaCO 3(s)  CaO (s) + O 2(g) 2 CaO (g) + 2 SO 2(g) + O 2(g)  2 CaSO 4(g) used to treat fruits and vegetables as a preservative

Tro, Chemistry: A Molecular Approach63 Sulfuric Acid most produced chemical in the world strong acid, good oxidizing agent, dehydrating agent used in production of fertilizers, dyes, petrochemicals, paints, plastics, explosives, batteries, steel, and detergents melting point 10.4  C, boiling point 337  C oily, dense liquid at room temperature reacts vigorously and exothermically with water “you always oughter(sic) add acid to water”

Tro, Chemistry: A Molecular Approach64 Dehydration of Sucrose C 12 H 22 O 11(s) + H 2 SO 4 (l)  12 C(s) + 11 H 2 O(g) + H 2 SO 4 (aq)

Tro, Chemistry: A Molecular Approach65 Production of H 2 SO 4 contact process step 1: combustion of elemental S complete using V 2 O 5 catalyst S (g) + O 2(g)  SO 2(g) 2 SO 2(g) + O 2(g)  2 SO 3(g) step 2: absorbing the SO 2 into conc. H 2 SO 4 to form oleum, H 2 S 2 O 7 SO 3(g) + H 2 SO 4(l)  H 2 S 2 O 7(l) step 3: dissolve the oleum in water H 2 S 2 O 7(l) + H 2 O (l)  2 H 2 SO 4(aq)

Tro, Chemistry: A Molecular Approach66 Halogens most reactive nonmetal group, never found in elemental form in nature come from dissolved salts in seawater except fluorine, which comes from minerals fluorospar (CaF 2 ) and fluoroapatite [Ca 10 F 2 (PO 4 ) 6 ] atomic radius increases down the column most electronegative element in its period, decreasing down the column fluorine only has oxidation states of -1 or 0, others have oxidation states ranging from -1 to +7

Tro, Chemistry: A Molecular Approach67 Properties of the Halogens

Tro, Chemistry: A Molecular Approach68 Fluorine F 2 is a yellow-green toxic gas F 2 is the most reactive nonmetal and forms binary compounds with every element except He, Ne, and Ar including XeF 2, XeF 6, XeOF 4, KrF 2 so reactive it reacts with other elements of low reactivity resulting in flames even reacts with the very unreactive asbestos and glass  stored in Fe, Cu, or Ni containers because the metal fluoride that forms coats the surface protecting the rest of the metal F 2 bond weakest of the X 2 bonds, allowing reactions to be more exothermic small ion size of F − leads to large lattice energies in ionic compounds produced by the electrolysis of HF

Tro, Chemistry: A Molecular Approach69 Hydrofluoric Acid HF produced by the reaction of fluorospar with H 2 SO 4 CaF 2(s) + H 2 SO 4(l)  CaSO 4(s) + 2 HF (g) crystalline HF is zig-zag chains HF is weak acid, K a = 6.8 x at 25  C F − can combine with HF to form complex ion HF 2 −  with bridging H strong oxidizing agent  strong enough to react with glass, so generally stored in plastic  used to etch glass SiO 2(g) + 4 HF (aq)  SiF 4(g) + H 2 O (l) very toxic because it penetrates tissues and reacts with internal organs and bones

Tro, Chemistry: A Molecular Approach70 Halogen Compounds form ionic compounds with metals and molecular compounds having covalent bonds with nonmetals halogens can also form compounds with other halogens – called interhalides for interhalides, the larger has lower electronegativity – so it is central in the molecule; with a number of more electronegative halides attached general formula AB n where n can be 1, 3, 5, or 7  most common AB or AB 3 ; only AB 5 has B = F, IF 7 only known n = 7 only ClF 3 used industrially  to produce UF 6 in nuclear fuel enrichment most halogen oxides are unstable tend to be explosive OF 2 only compound with O = +2 oxidation state ClO 2(g) is strong oxidizer used to bleach flour and wood pulp  explosive – so diluted with CO 2 and N 2  produced by oxidation of NaClO 2 with Cl 2 or the reduction of NaClO 3 with HCl 2 NaClO 2 + Cl 2  2 NaCl + 2 ClO 2 2 NaClO HCl  2 ClO H 2 O + 2 NaCl