Insert picture from First page of chapter Chapter 24 Nonmetallic Elements and Their Compounds Copyright McGraw-Hill 2009 1 24.1 General Properties of Nonmetals • Properties of nonmetals - more varied than those of metals • Physical state – Gases: hydrogen, oxygen, nitrogen, fluorine, chlorine, and the noble gases – Liquid : bromine – Solids: All the remaining nonmetals • Poor conductors of heat and electricity • Exhibit either positive or negative oxidation numbers. Copyright McGraw-Hill 2009 2 • Metalloids - small group of elements have properties characteristic of both metals and nonmetals. • More electronegative than metals • Electronegativity increases from left to right across any period and from bottom to top in any group in the periodic table • With the exception of hydrogen, the nonmetals are concentrated in the upper right-hand corner of the periodic table • Compounds formed by a combination of metals with nonmetals tend to be ionic, having a metallic cation and a nonmetallic anion. Copyright McGraw-Hill 2009 3 Nonmetals and Metalloids on the Periodic Table Nonmetals coded in blue and metalloids in orange.. Copyright McGraw-Hill 2009 4 24.2 Hydrogen • Simplest known element • Exists as a diatomic molecule • H2 is a colorless, odorless, and nonpoisonous gas. • At 1 atm, boiling point is −252.9°C (20.3 K). • Most abundant element in the universe Copyright McGraw-Hill 2009 5 • Ground-state electron configuration: 1s1. – Resembles the alkali metals (Group 1A) in that it can be oxidized to the H+ ion, which exists in aqueous solutions in the hydrated form. – Resembles the halogens (Group 7A) in that it forms the hydride • H− (hydride ion) - isoelectronic with helium (1s2) • Found in a large number of covalent compounds. • Unique capacity to form hydrogen bonds Copyright McGraw-Hill 2009 6 • Preparation – Industrial scale – Laboratory scale Copyright McGraw-Hill 2009 7 Laboratory Generation of Hydrogen Copyright McGraw-Hill 2009 8 • Binary hydrides - compounds containing hydrogen and another element, either a metal or a nonmetal. • Types of hydrides – Ionic hydrides direct combination of molecular hydrogen and any alkali or alkaline earth metal – Solids with high melting points – Contain the strong BrØnsted base, H− Copyright McGraw-Hill 2009 9 – covalent hydrides - the hydrogen atom is covalently bonded to the atom of another element • Types of covalent hydrides –Discrete unit structure – NH3 –Polymeric structure – (BeH2)x – Interstitial hydrides – compounds of hydrogen and transition metal in which the atomic ratio is not constant – titanium hydride ranges from TiH1.8 to TiH2. Copyright McGraw-Hill 2009 10 Binary Hydrides of Representative Elements Copyright McGraw-Hill 2009 11 • Isotopes of hydrogen – Hydrogen has three naturally occurring isotopes – 11H, hydrogen, (99.985%) – 21H , deuterium, symbol D, (0.015%) 3 – 1H , tritium, symbol T, (radioactive, t1/2 =12.5 years. – Deuterium containing water, D2O • Called heavy water or deuterated water • Toxic • Affects reaction rates – isotopic effect Copyright McGraw-Hill 2009 12 Copyright McGraw-Hill 2009 13 • Hydrogenation - addition of hydrogen to compounds containing multiple bonds, usually carbon to carbon double or triple bonds. – Catalyzed by metals (Pt or Cd) – Important in food industry Copyright McGraw-Hill 2009 14 • Hydrogen Economy – Hydrogen an alternative fuel source to petroleum fuels • For automobiles • Electrical power generation – Pollution free fuel – Present dilemma – how to obtain sufficient amounts of H2 – Splitting water using solar energy – one possible source for the needed H2. Copyright McGraw-Hill 2009 15 24.3 Carbon • 0.09 % by mass of Earth’s crust • An essential element of living matter • A component of natural gas, petroleum and coal. • Combines with oxygen to form carbon dioxide in the atmosphere • Occur as carbonates in limestone and chalk. • Found free in allotropic forms of diamond and graphite Copyright McGraw-Hill 2009 16 Phase Diagram for Allotropic Forms of Carbon Copyright McGraw-Hill 2009 17 • catenation – carbon has the unique ability to form long chains stable rings – Responsible for the millions of carboncontaining compounds • Reacts with – Metals to form carbides (strong bases), CaC2 – Silicon to form carborundum, SiC – Nitrogen to form cyanides, C N • Toxic • Readily complexes metals Copyright McGraw-Hill 2009 18 Cyanide Pond for Extracting Gold Copyright McGraw-Hill 2009 19 • Important oxides – Carbon monoxide (CO) • Formed during incomplete combustion • Colorless, odorless gas • Used in metallurgical processes • Used in organic synthesis • Not acidic • Only slightly soluble in water • Burns to produce carbon dioxide Copyright McGraw-Hill 2009 20 – Carbon dioxide (CO2) • Colorless and odorless gas • Nontoxic—although it is a simple asphyxiant • Acidic oxide – forms carbonic acid • Uses – “carbonated” beverages –Fire extinguishers –Manufacture of baking soda (NaHCO3) –Manufacture of soda ash (Na2CO3) –“Dry ice” as a refrigerant Copyright McGraw-Hill 2009 21 24.4 Nitrogen and Phosphorous • Nitrogen – Mineral sources of nitrogen: saltpeter (KNO3) and Chile saltpeter (NaNO3) – Nitrogen is an essential element of life • A component of proteins and nucleic acids – N2 is obtained by the fractional distillation of air – N2 contains a triple bond and is stable – Forms variable oxidation states Copyright McGraw-Hill 2009 22 Copyright McGraw-Hill 2009 23 • Common (important) forms of nitrogen – Nitride ion, N3−, a strong BrØnsted base – Ammonia, NH3 • Undergoes autoionization to produce the highly basic amide ion, NH2- – Hydrazine, N2H4 • Basic • Reducing Agent Copyright McGraw-Hill 2009 24 • Important oxides – Nitrous oxide (N2O) • Supports combustion • Used as dental anesthetic – Nitric oxide (NO) • Produced in atmosphere (form of nitrogen fixation) • Colorless gas • Produced in auto exhaust • Paramagnetic • Resonance stabilized Copyright McGraw-Hill 2009 25 – Nitrogen Dioxide (NO2) • Toxic • Paramagnetic • Dimerizes to N2O4 in the liquid and gas phases • Acidic oxide –Shown in a disproportionation reaction with cold water Copyright McGraw-Hill 2009 26 • Nitric acid (HNO3) – Powerful oxidizing agent – Can be reduced to NH4+ – Aqua regia – 1:3 mixture of concentrated HCl and concentrated HNO3 • Even oxidizes gold – Oxidizes nonmetals to oxoacids – Used in manufacture of • Fertilizers • Drugs • Explosives • Dyes Copyright McGraw-Hill 2009 27 • Phosphorus – Occurs most commonly in nature as phosphate rocks • calcium phosphate [Ca3(PO4)2] • fluoroapatite [Ca5(PO4)3F] – Elemental phosphorus produced by Ca5(PO4)3F – Allotropic forms of phosphorus • Red phosphorus • White phosphorus Copyright McGraw-Hill 2009 28 Allotropes of Phosphorus Copyright McGraw-Hill 2009 29 – Reactions of phosphorus • Formation of phosphine (PH3) • Formation of phosphoric acid • Reaction with the halogens Copyright McGraw-Hill 2009 30 • Acid production from halides • Reaction with oxygen to produce acidic oxides Copyright McGraw-Hill 2009 31 Structure of P4O6 and P4O10 Copyright McGraw-Hill 2009 32 • Oxoacids of phosphorus Copyright McGraw-Hill 2009 33 24.5 Oxygen and Sulfur • Oxygen – Most abundant element in Earth’s crust (46% by mass) – Atmosphere contains about 21% by volume (23% by mass) – Diatomic molecule (O2) in the free state – Essential for human life – Alloptropic forms: O2 and O3 (ozone) – Strong oxidizing and bleaching agent Copyright McGraw-Hill 2009 34 – Oxides • Types of oxides –Normal oxide, O22− –Peroxide, O22− –Superoxide, O2− • All are strong BrØnsted bases Copyright McGraw-Hill 2009 35 • Bonding in oxides – ionic to covalent left to right on the periodic table • Acid-base character of oxides – Basic Amphoteric Acidic –Basicity increases down a group – Peroxides • H2O2 (hydrogen peroxide) – most common example Copyright McGraw-Hill 2009 36 Structure of H2O2 Copyright McGraw-Hill 2009 37 • Polar • Miscible with water • Decomposes spontaneously • Used as mild antiseptic (3% solution) or bleach agent (higher concentrations) • Used as rocket fuel due to high heat of decompostion • Serves as an oxidzing agent • Serves as a reducing agent Copyright McGraw-Hill 2009 38 – Ozone • Toxic, light-blue gas • Pungent odor • Essential component of the atmosphere • Structure • Powerful oxidizing agent • Preparation Copyright McGraw-Hill 2009 39 Preparation of O3 Copyright McGraw-Hill 2009 40 • Sulfur – Constitutes about 0.06 % of Earth’s crust by mass – Occurs commonly in nature in the elemental form • Sedimentary deposits • Gypsum (CaSO4. 2H2O) and various sulfide minerals such as pyrite (FeS2) – Most common allotropic forms • Monoclinic • Rhombic – most stable form – S8 Copyright McGraw-Hill 2009 FeS2 41 Puckered Ring of S8 Copyright McGraw-Hill 2009 42 – Extracted by the Fasch process Copyright McGraw-Hill 2009 43 – Forms wide variety of oxidation numbers Copyright McGraw-Hill 2009 44 – Hydrogen sulfide – H2S • Used in qualitative analysis • Preparation • Colorless gas with odor of rotten eggs • Toxic • Weak diprotic acid • Reducing agent in basic solution Copyright McGraw-Hill 2009 45 – Oxides of sulfur • Sulfur dioxide (SO2) –Pungent colorless gas –Toxic –Preparation –Acidic oxide –Oxidation Copyright McGraw-Hill 2009 46 • Sulfur trioxide (SO3) –Involved in acid rain –Used in the production of sulfuric acid (H2SO4) in the contact process* *Vanadium(V) oxide (V2O5) is the catalyst used for the key second step. Copyright McGraw-Hill 2009 47 • Sulfuric acid –Diprotic acid –Colorless, viscous liquid (m.p. 10.4°C) –Concentrated sulfuric acid is 98 % H2SO4 by mass (density 1.84 g/cm3), 18 M. –Oxidizing strength of sulfuric acid depends on temperature and concentration. –Cold dilute sulfuric acid reacts with active metals Copyright McGraw-Hill 2009 48 –Hot concetrated sulfuric acid reacts with less active metals –Depending on the reducing agent, sulfate may be reduced –Oxidizes nonmetals Copyright McGraw-Hill 2009 49 • Carbon disulfide (CS2) –Colorless, flammable liquid (b.p. 46°C) –Preparation –SIightly soluble in water –Solvent for nonpolar substances • Sulfur hexafluoride (SF6) – Preparation – Colorless, nontoxic, inert gas Copyright McGraw-Hill 2009 50 24.6 The Halogens • The halogens—fluorine, chlorine, bromine, and iodine—are reactive nonmetals. Copyright McGraw-Hill 2009 51 • All are highly reactive and toxic • Magnitude of reactivity and toxicity generally decreases from fluorine to iodine. • The chemistry of fluorine differs from that of the rest of the halogens in the following ways: – Fluorine is the most reactive due to the relative weakness of the F−F bond. – The difference in reactivity between fluorine and chlorine is greater than that between chlorine and bromine. Copyright McGraw-Hill 2009 52 – Hydrogen fluoride (HF) has a relatively high boiling point (19.5°C) – Hydrofluoric acid is a weak acid, all other hydrohalic acids are strong acids. – Fluorine uniquely reacts with cold sodium hydroxide solution to produce oxygen difluoride as follows: – Silver fluoride (AgF) is soluble. All other silver halides (AgCl, AgBr, and AgI) are insoluble. Copyright McGraw-Hill 2009 53 • Elemental state, halogens form diatomic molecules (X2). • In nature, always found combined with other elements. – Chlorine, bromine, and iodine occur as halides in seawater – Fluorine occurs in the minerals fluorite (CaF2) and cryolite (Na3AlF6). • All isotopes of astatine (As) are radioactive Copyright McGraw-Hill 2009 54 • Preparation and Properties of F2 and Cl2 – determined by their strong oxidizing capability – Fluorine • From liquid HF • At 70oC Copyright McGraw-Hill 2009 55 Electrolytic Preparation of F2 Copyright McGraw-Hill 2009 56 – Chlorine • Electrolysis of molten NaCl • Overall reaction • Chlor-alkali process –Designed to prevent side reactions –Mercury cell –Diaphragm cell Copyright McGraw-Hill 2009 57 Mercury Cell in the Chlor-alkali Process Copyright McGraw-Hill 2009 58 Diaphragm Cell in the Chlor-alkali Process Copyright McGraw-Hill 2009 59 • Compounds of the Halogens – Either ionic or covalent. • The fluorides and chlorides especially those belonging to the alkali metal and alkaline earth metal are ionic compounds (except halides of Be). • Most of the halides of nonmetals are covalent compounds. – Oxidation numbers range from −1 to +7 except F which can only be 0 (in F2) and −1, in all compounds. Copyright McGraw-Hill 2009 60 – Hydrogen Halides • Preparation from elements – can occur violently • Preparation varies with the halogen, for example HCl HF HBr Copyright McGraw-Hill 2009 61 – Industrial uses of hydrogen fluoride (HF) • Reactive enough to etch glass • Used in the manufacture of Freons – Industrial uses of hydrogen chloride (HCl) • Preparation of hydrochloric acid • Inorganic chlorides • Various metallurgical processes Copyright McGraw-Hill 2009 62 – Aqueous solutions of HX • Acidic • Variation in acid strength – Oxoacids – halogens form a series of acids increasing acid strength • Only Cl forms the entire series Copyright McGraw-Hill 2009 63 Copyright McGraw-Hill 2009 64 • Uses of the halogens – Fluorine • UF6 separating isotopes of U • Production of polytetrafluorethyline (Teflon ©) – Chlorine • Biological role as Cl−(aq) • Industrial bleaching – Cl2 • Water purification – Cl2, ClO− • Organic solvents – CHCl3 • Polymer production - PVC Copyright McGraw-Hill 2009 65 – Bromine • Insecticides (BrCH2CH2Br) • Scavenger for Pb in gasoline • Photographic films (AgBr) – Iodine • Antiseptic (tincture of iodine) • Thyroxine (thyroid hormone derivative) • Cloud seeding (AgI) Copyright McGraw-Hill 2009 66 Key Points • General properties of the nonmetals • Hydrogen – Properties – Preparation – Binary Halides • Ionic • Covalent • Interstitial Copyright McGraw-Hill 2009 67 – Isotopes of hydrogen • Hydrogen (protium) • Deuterium • Tritium – Hydrogenation – The hydrogen economy • Carbon – Properties – Allotropes • Diamond • Graphite Copyright McGraw-Hill 2009 68 – Carbides – Cyanides – Oxides • Carbon monoxide • Carbon dioxide • Nitrogen and Phosphorus – Nitrogen • • • • Properties Nitrides Ammonia Hydrazine Copyright McGraw-Hill 2009 69 • Oxides –Nitrous oxide –Nitric oxide –Nitrogen dioxide • Nitric Acid – Phosphorus • Properties • Allotropes –White phosphorus –Red phosphorus • Phosphine • Halogen compounds Copyright McGraw-Hill 2009 70 • Oxides • Oxoacids • Oxygen and Sulfur – Oxygen • Properties • Allotropes • Oxides –Normal oxide –Peroxide –Superoxide • Acidity of oxides Copyright McGraw-Hill 2009 71 • Hydrogen peroxide • Ozone – Sulfur • Properties • Industrial production • Hydrogen sulfide • Oxides –Sulfur dioxide –Sulfur trioxide • Sulfuric Acid –Production –Uses Copyright McGraw-Hill 2009 72 • Carbon disulfide • Sulfur hexafluoride • The Halogens – Properties • Special properties of fluorine – Preparation and Properites • Preparation of fluorine • Preparation of chlorine – chlor-alkali process –Mercury Cell –Diaphragm cell Copyright McGraw-Hill 2009 73 • Hydrogen Halides • Oxoacids – Uses of the halogens • Fluorine • Chlorine • Bromine • Iodine Copyright McGraw-Hill 2009 74