Chapter 22 Chemistry of the Nonmetals

Transcription

1 Chapter 22 Chemistry of the Nonmetals

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3 Chapter 22.1 PERIODIC TRENDS AND CHEMICAL REACTIONS Nonmetals Except for hydrogen, the nonmetals are found in the upper right-hand corner of the periodic chart.

4 Chapter 22.1 PERIODIC TRENDS AND CHEMICAL REACTIONS Periodic Trends Within a group, smaller atoms are more likely to form -bonds because they can get closer to other atoms. Only 2 nd period elements readily form -bonds.

5 Chapter 22.1 PERIODIC TRENDS AND CHEMICAL REACTIONS Periodic Trends As a result, CO 2 contains two -bonds, and SiO 2 is a network solid with only -bonds.

6 (a) N (b) K (c) P (d) N (a) Cs (b) Cl (c) C (d) Sb

7 Chapter 22.2 HYDROGEN Hydrogen The most abundant element in the universe. The nuclear fuel for the Sun and other stars Constitutes 75% of the known mass of the universe and 0.9% of Earth s mass. There are three isotopes: Protium ( 1 H): 99.98% of all hydrogen Deuterium ( 2 H): 0.016% of all hydrogen Tritium ( 3 H): trace, radioactive They have different mp, bp, and density

8 Chapter 22.2 HYDROGEN Properties of Hydrogen Hydrogen is unique. It does not belong to any group. It has very low melting ( 259 C) and boiling ( 253 C) points (weak intermolecular interaction). It has very large bond enthalpies. 436 kj/mol (242 kj/mol for Cl-Cl) It reacts slowly and requires catalysts. Its reactions are generally quite exothermic.

9 Chapter 22.2 HYDROGEN Hydrogen Production Hydrogen is commercially produced from reaction of methane (CH 4 ) with steam at 1100 C or carbon and steam above 1000 C. CH 4 (g) + H 2 O(g) CO(g) + 3 H 2 (g) CO(g) + H 2 O(g) CO 2 (g) + H 2 (g) C(s) + H 2 O(g) H 2 (g) + CO(g) Its production from the electrolysis of water is not energy efficient.

10 Chapter 22.2 HYDROGEN Uses of Hydrogen Most hydrogen (70%) is used to produce ammonia (NH 3 ) in the Haber process. It is also used to produce methanol (CH 3 OH). CO(g) + 2 H 2 (g) CH 3 OH(g)

11 Chapter 22.2 HYDROGEN Uses of Hydrogen 2 H 2 (g) + O 2 (g) 2 H 2 O(g) H = kj Using hydrogen as a fuel would have many advantages: It's reaction with oxygen is highly exothermic. Water is the only product Cheap and efficient production of hydrogen is important

12 Hydrides Hydrogen-containing compounds There are three types of hydrides: Ionic Metallic Molecular Chapter 22.2 HYDROGEN

13 Ionic Hydrides Chapter 22.2 HYDROGEN Ionic hydrides are formed between hydrogen and alkali metals or heavy alkaline earth metals (Ca, Sr, Ba). They are very strong bases and reducing agents. They react readily with water, so they must be stored free from moisture.

14 Chapter 22.2 HYDROGEN Metallic Hydrides These are formed between hydrogen and transition metals, often in unusual ratios. TiH 1.8, for example. They retain electrical conductivity and other metallic properties.

15 Chapter 22.2 HYDROGEN Molecular Hydrides These are formed between hydrogen and nonmetals or metalloids. They are usually gases or liquids at room temperature and normal atmospheric pressure.

16 Chapter 22.3 GROUP 8A: THE NOBEL GASES Noble Gases Noble gases are extremely stable and unreactive. Liquid He (boiling point 4.2 K) is used as a coolant. Ne is used in electric signs. Ar is used in light bulbs and as an insulating gas between panes in thermal windows.

17 Xenon Compounds Of all noble gases, Xe can be forced to form compounds most easily. KrF 2 is also known, but decomposes at 10 C. Chapter 22.3 GROUP 8A: THE NOBEL GASES

18 Chapter 22.4 GROUP 7A: THE HALOGENS Halogens Large electron affinities and ionization energies Outer electron configurations of ns 2 np 5. They tend to accept one electron to form anions All have a 1 oxidation state. All but fluorine also have positive oxidation states up to +7 when bonded to more electronegative atoms such as O.

19 Properties of Halogens Chapter 22.4 GROUP 7A: THE HALOGENS They tend to be good oxidizers, due to their electronegativity. They can oxidize anions of halides below them on periodic chart. H 2 O CCl 4 NaI.

20 Properties of Halogens Fluorine has an unusually high reduction potential. It can easily oxidize water. Chapter 22.4 GROUP 7A: THE HALOGENS F 2 (aq) + H 2 O(l) 2 HF(aq) + 1/2 O 2 (g) E = 1.80 V Fluorine is formed by electrolytic oxidation of a solution of KF in anhydrous HF Chlorine is produced mainly by electrolysis of either molten or aqueous sodium chloride

21 Chapter 22.4 GROUP 7A: THE HALOGENS Uses of Halogens Fluorine reacts to form fluorocarbon compounds used as lubricants, refrigerants and plastics. Teflon is a polymer of fluorocarbons with high thermal/chemical stability. Teflon has one of the lowest coefficients of friction against any solid

22 Chapter 22.4 GROUP 7A: THE HALOGENS Uses of Halogens Chlorine is the most-used halogen. HCl Plastics (PVC) Bleaches (NaOCl) Water purification (Cl 2 ) PVC

23 Chapter 22.4 GROUP 7A: THE HALOGENS Uses of Halogens Bromine is the anion for silver in photographic film. KI is added to table salt as a dietary supplement. Thyroxine goiter (thyroid gland swelling)

24 Chapter 22.4 GROUP 7A: THE HALOGENS Hydrogen Halides Aqueous solutions of HCl, HBr, and HI are, of course, strong acids. HF and HCl can be produced by reacting salts (CaF 2 /CaCl 2 ) with H 2 SO 4. Br and I are oxidized too easily, so one must use a weaker oxidizing acid, like H 3 PO 4. Oxidation of NaI & NaBr by H 2 SO 4. NaI NaBr

25 Hydrofluoric Acid Chapter 22.4 GROUP 7A: THE HALOGENS Hydrofluoric acid reacts with silicates, components of most types of glass. This reaction causes glass to etch. Therefore, HF is usually stored in plastic containers. Interhalogen compounds such as ClF, IF 5, IF 7 and ICl 3 are powerful oxidizing agents.

26 Oxyacids and Oxyanions Chapter 22.4 GROUP 7A: THE HALOGENS Oxyacid strength increases with the increasing oxidation number of the central halogen. Oxyacids are strong oxidizers. Oxyanions generally more stable than the corresponding acids.

27 Oxyacids and Oxyanions While generally quite stable, perchlorates become exceedingly strong oxidizers when heated, and are used as a rocket fuel (NH 4 ClO 4 /Al powder) 700 tons of NH 4 ClO 4 are required for each shuttle launch Chapter 22.4 GROUP 7A: THE HALOGENS

28 Chapter 22.5 OXYGEN Oxygen Joseph Priestley discovered oxygen in Lavoisier give it its name, which means acid former. The most abundant element by mass both in earth s crust and in the human body Most commercial oxygen is obtained from air.

29 Chapter 22.5 OXYGEN Oxygen It exists as one of two allotropes, O 2 and O 3. Bp -183 C; mp -218 C for O 2. Water solubility 0.04 g/l (0.001 M) at 25 C. It forms very strong bonds. The bond enthalpy of O 2 is 495 kj/mol. The reactions of oxygen-containing compounds have high activation energies. Its reactions can be very exothermic, even to point of being explosive.

30 Chapter 22.5 OXYGEN Uses of Oxygen Most notably, oxygen is an oxidizing agent. Bleach pulp and paper Medical uses (eases breathing difficulties) Welding (with acetylene) a highly exothermic reaction

31 Ozone It is a bluish gas with a sharp, irritating odor. It is extremely irritating to respiratory system. It is a stronger oxidizer than O 2. It is used to purify water It is used in organic synthesis. Protection from UV Prepared from O 2 by electricity. Chapter 22.5 OXYGEN

32 Oxides Chapter 22.5 OXYGEN Oxygen is second-most electronegative element. It always has a negative oxidation state except when bonded to F. Acidic oxides like SO 2, CO 2 and SO 3 form acids when exposed to water. Basic oxides like BaO form hydroxide ion when they react with water.

33 Peroxides Chapter 22.5 OXYGEN Compounds containing O O bonds and oxygen in an oxidation state of -1 are called peroxides. The O O bond very weak. The decomposition of peroxides can be dangerously exothermic disproportionation reaction 3% H 2 O 2, a mild antiseptic. a byproduct of metabolism; peroxidase and catalase.

34 Superoxides In superoxides (O 2- ) oxygen has oxidation state of 1/2. The most active metals (K, Rb, Cs) form superoxides through reaction with O 2. The next active metals produces peroxides (Na 2 O 2, CaO 2, SrO 2,and BaO 2 ) They react with H 2 O to form O 2. It is the source of O 2 in selfcontained breathing devices. Chapter 22.5 OXYGEN

35 Other Group 6A Elements Elements in this group have The general outer-e configuration is ns 2 np 2 Oxidation states of 2 as well as several positive oxidation states (SF 6, SeF 6, and TeF 6 ). They can have expanded octets. Chapter 22.6 OTHER GROUP 6A ELEMENTS

36 Selenium and Tellurium Chapter 22.6 OTHER GROUP 6A ELEMENTS These elements are anions in minerals with Cu, Pb, Ag, and Au. They are naturally found as helical chains of atoms. Selenium is not electrically conductive in dark, but quite so in light. Therefore, it is used in light meters, photosensors, and photocopiers.

37 Chapter 22.6 OTHER GROUP 6A ELEMENTS Sulfur Sulfur is a solid, yellow compound found as an 8-membered ring in nature. As it is heated to melting (113 C), the ring breaks and the sulfur becomes a viscous, reddish-brown liquid.

38 Chapter 22.6 OTHER GROUP 6A ELEMENTS Sulfur Most sulfur is used either for the production of H 2 SO 4 or for the vulcanization of rubber. or Schematic presentation of two strains (blue and green) of natural rubber after vulcanization with elemental sulfur

39 Sulfides Pyrites contain the disulfide ion, S 2 2, the sulfur analog of peroxide. It is found in minerals like iron pyrite (fool s gold). One of hydrogen sulfide s readily recognized properties is its odor. H 2 S is toxic and emitted by rotten eggs. Dimethyl sulfide is added to natural gas as a safety factor Many minerals like galena (PbS) and cinnabar (HgS) are sulfides. Chapter 22.6 OTHER GROUP 6A ELEMENTS Iron pyrite (FeS 2 ) 황철광

40 Chapter 22.6 OTHER GROUP 6A ELEMENTS Sulfur Oxides, Oxyacids, and Oxyanions SO 2 is a poison, particularly to lower organisms. It is used to sterilize dried fruit and wine. It does this by dissolving in H 2 O to form H 2 SO 3. Sulfites and bisulfites are added to foods and wines to kill bacteria (Na 2 SO 3, NaHSO 3 ).

41 Sulfuric Acid Chapter 22.6 OTHER GROUP 6A ELEMENTS SO 3 is important for the production of H 2 SO 4. Sulfuric acid is a strong acid, good dehydrating agent, and decent oxidizer. 2009, Prentice-Hall, Inc.

42 Chapter 22.7 NITROGEN Nitrogen Nitrogen was discovered in 1772 by Daniel Rutherford. It makes up 78% of Earth s atmosphere. mp -210 C, bp -196 C It can exist in oxidation states from 3 to +5. The bond enthalpy of N N is 941 kj/mol.

43 Chapter 22.7 NITROGEN Nitrogen N 2 is obtained in commercial quantities by fractional distillation by liquid air. Many nitrogen-containing compounds are strong oxidizers. N 2 is used in the Haber process. Also used as a coolant to freeze foods rapidly. NH 3 is a precursor to many other compounds.

44 NH 3 is one of the most important compounds of nitrogen. Colorless and toxic; characteristic irritating odor About 75% of NH 3 produced is used for fertilizer. Hydrazines are made from ammonia. Chapter 22.7 NITROGEN Hydrogen Compounds of Nitrogen One intermediate in the process is chloramine (NH 2 Cl), the poisonous compound produced when household ammonia and hypochlorite ion in bleach are mixed. Hydrazines are strong reducers used in rocket fuels.

45 Nitrogen Oxides and Oxyacids Chapter 22.7 NITROGEN Nitrous oxide (N 2 O, laughing gas) was the first general anesthetic. Nitric oxide (NO) is a slightly toxic, colorless gas. It has recently been shown to be a neurotransmitter involved in vasodilation in humans. It reacts with O 2 in the air to produce nitrogen dioxide, NO 2.

46 An interesting observation in Alfred Nobel s dynamite factories. Angina pectoris ( 협심증 ): severe chest pain due to a lack of blood (oxygen) of the heart muscle Conversion of nitroglycerin into NO increases passage of blood in the heart muscle. In 1998, the Nobel Prize was awarded to the discoveries. Prolonged administration results in development of tolerance or desensitization.

47 Nitrogen Oxides and Oxyacids Chapter 22.7 NITROGEN Nitric acid is A strong acid and oxidizer. Used in fertilizer and explosive production (TNT, nitrocellulose, nitroglycerine). Nitrous acid is A less stable, yet weaker acid than HNO 3. TNT nitrocellulose

48 Other Group 5A Elements Chapter 22.8 THE OTHER GROUP 5A ELEMENTS This group contains nonmetals (N and P), a metal (Bi), and metalloids (As and Sb).

49 Chapter 22.8 THE OTHER GROUP 5A ELEMENTS Phosphorus There are two allotropes of phosphorus: White phosphorus (P 4 ) - Is highly strained, and - Bursts into flames if exposed to O 2 in the air. Red phosphorus, - Made from P 4 by heating without air - Amorphous network, stable

50 Phosphorus Halides Chapter 22.8 THE OTHER GROUP 5A ELEMENTS The trihalides and pentahalides are important. PCl 3 is commercially the most significant of these compounds and used to prepare a wide variety of products White or red If excess chlorine gas is present, an equilibrium is established between PCl 3 and PCl 5

51 Chapter 22.8 THE OTHER GROUP 5A ELEMENTS Oxyphosphorus Compounds Phosphorus(III) oxide (P 4 O 6 ) and phosphorus(v) oxide (P 4 O 10 ) are anhydride forms of phosphorous (H 3 PO 3 ) and phosphoric (H 3 PO 4 ) acids. Used on match tips detergents fertilizers drying agent high affinity for water

52 Oxyphosphorus Compounds Phosphorus compounds are important in biological systems RNA and DNA are polymerized by the phosphoric diester bond. ATP: energy storage Chapter 22.8 THE OTHER GROUP 5A ELEMENTS

53 Carbon Found in CaCO 3, coal, petroleum and natural gas. Important in all living organisms Carbon has four allotropes: Graphite, Diamond, Fullerenes, and Carbon nanotubules. Graphite is converted to diamond (at 100,000 atm and 3000 C) for industrial uses. Activated charcoal is used to adsorb molecules. Chapter 22.9 CARBON

54 Carbon Oxides Chapter 22.9 CARBON Carbon monoxide (CO) This is an odorless, colorless gas. CO binds preferentially to iron in hemoglobin, inhibiting O 2 transport. It is used as a fuel, a reducing agent in metallurgy, and a precursor to organic compounds. Carbon dioxide (CO 2 ) This common gas is used to carbonate beverages, decaffeinate products (in its supercritical form), and as a refrigerant (as Dry Ice ). Washing soda (Na 2 CO 3 ), baking soda (NaHCO 3 )

55 Carbonic Acid and Carbonates Dissolved CO 2 in water is in equilibrium with carbonic acid, H 2 CO 3. Carbonates are found as minerals like calcite, CaCO 3, the primary constituent of limestone. Chapter 22.9 CARBON

56 The Group 4A Elements Chapter THE OTHER GROUP 4A ELEMENTS The electronegativities of the elements are generally low. C, Si, Ge, Sn, and Pb

57 Chapter THE OTHER GROUP 4A ELEMENTS Silicon Silicon is the second most abundant element in Earth s crust. It is a semiconductor used in making transistors and solar cells. It is purified by a process known as zonerefining.

58 Chapter THE OTHER GROUP 4A ELEMENTS Silicates Silicates have a central silicon atom that is surrounded by four oxygens. In disilicate, two tetrahedral structures share one oxygen. Silicate Disilicate

59 Chapter THE OTHER GROUP 4A ELEMENTS Silicates asbestos 석면 활석 talc These units can further connect into sheets or strands. Talc and asbestos are two examples of molecules containing these structures. Mg 3 (SiO 2 O 5 )(OH) 4 Mg 3 Si 4 O 10 (OH) 2

60 Chapter THE OTHER GROUP 4A ELEMENTS Silicates Quartz (SiO 2, crystalline) - all four vertices of each SiO 4 tetrahedron are linked to other tetrahedra. Glass (amorphous) noncrystalline SiO 2 containing additives like Na 2 O and CaO.

61 Chapter BORON Boron Boron is the only nonmetallic Group 3A element. Compounds of boron and hydrogen are called boranes (BH 3, B 2 H 6 ). Because boron does not have a filled octet, structures such as diborane, in which two borons share one hydrogen, are possible.

62 Chapter BORON Boron Borane anions, such as borohydride, BH 4, are good reducing agents and sources of hydride ion (NaBH 4 ).