1. The Representative Elements Chapter 20 Lesson 2

2. 20.1A Survey of the Representative Elements 20.2 The Group 1A Elements 20.3 The Chemistry of Hydrogen 20.4The Group 2A Elements 20.5The Group 3A Elements 20.6 The Group 4A Elements The representative Elements: Groups 1A – 4A

3. The representative Elements: Groups 5A – 8A 20.7The Group 5A Elements 20.8 The Chemistry of Nitrogen 20.9The Chemistry of Phosphorus 20.10The Group 6A Elements 20.11The Chemistry of Oxygen 20.12The Chemistry of Sulfur 20.13The Group 7A Elements 20.14The Group 8A Elements

4. Valence-shell configuration: ns 2 np 4 O, S, Se, Te, Po None of the Group 6A elements behaves as a typical metal. Elements form covalent bonds with other nonmetals. Group 6A

5. Some Physical Properties, Sources, and Methods of Preparation

6. Oxygen O 2 makes up 21% of the Earth’s atmosphere. O 3 (ozone) exists naturally in the upper atmosphere (the stratosphere) of the Earth.  Ozone layer absorbs UV light and acts as a screen to block most uv-radiation from reaching the Earth’s surface.  We now know that Freons are promoting destruction of ozone layer.

7. Various Forms of Oxides Metal oxides (ionic) 1.Nonconductor – example: MgO 2.Semiconductor – example: NiO 3.Conductor – example: ReO 3 4.Superconductor – example: YBa 2 Cu 3 O 7 Nonmetal oxides (covalent): Molecular oxides – examples: CO 2, NO, NO 2, N 2 O, SO 2, P 4 O 10, etc. Covalent network oxide – SiO 2

8. Ozone 3O 2 (g)  2O 3 (g)

9. Characteristics of Oxides Metallic oxides – basic or amphoteric Examples: Na 2 O (basic); Al 2 O 3 (amphoteric) Semi-metallic oxides – mild to weakly acidic Example: B 2 O 3 Nonmetallic oxides – weak to strong acids Examples: 1.SO 2 (g) + H 2 O (l)  H 2 SO 3 (aq) (weak acid); 2.SO 3 (g) + H 2 O (l)  H 2 SO 4 (aq) (strong acid);

10. Sulfur is found in nature both in large deposits of the free element and in ores such as: Galena = PbS, Cinnabar = HgS, Pyrite = FeS 2, Gypsum = CaSO 4  2H 2 O), Epsomite = MgSO 4.7H 2 O, and Glauberite = Na 2 Ca(SO 4 ) 2 Sulfur

11. Sulfur Mining: Frasch Process

12. Sulfuric Acid Productions: 1.S 8 (s) + 8 O 2 (g)  8SO 2 (g) ; 2.2H 2 S (g) + 3 O 2 (g)  2SO 2 (g) + 2H 2 O (l) ; 3.FeS 2 (s) + 11 O 2 (g)  Fe 2 O 3 (s) + 8SO 2 (g) ; 1.2SO 2 (g) + O 2 (g)  2SO 3 (g) ; (V 2 O 5 /K 2 O catalyst) 2.2SO 3 (g) + H 2 SO 4 (l)  H 2 S 2 O 7 (l) ; 3.H 2 S 2 O 7 (l) + H 2 O (l)  2H 2 SO 4 (l) ;

13. Important Compounds of Sulfur H 2 SO 4 – most important compound, for manufacture of fertilizer, soap, detergents, metal and textile processing, sugar refinery, and organic syntheses; SF 4 – for fluoridation SF 6 – as insulating and inert blanket Na 2 S 2 O 3 – as reducing agent and complexing agent for Ag + in photography (called “hypo”); P 4 S 3 – in “strike-anywhere” match heads

14. The Halogens All nonmetals: F, Cl, Br, I, At Most reactive nonmetal group; Not found as free elements in nature. Mainly found as halide ions (X – ) in various minerals and in seawater.

15. Trends in Selected Physical Properties

16. Preparation of Hydrogen Halides H 2 (g) + X 2 (g)  2HX (g) When dissolved in water, the hydrogen halides behave as acids, and all except hydrogen fluoride are completely dissociated.

17. Halogen Oxyacids and Oxyanions All halogens except fluorine combine with various numbers of oxygen atoms to form oxyacids. Strengths of oxyacids vary directly to the number of oxygen atoms bonded to the halogen - acid strength increases as more oxygens are added.

18. The Known Oxyacids of the Halogens

19. Interhalogen Compounds Formation: Cl 2 (g) + 3F 2 (g)  2ClF 3 (g) ; Br 2 (l) + 3F 2 (g)  2BrF 3 (l) ; Br 2 (l) + 5F 2 (g)  2BrF 5 (l) ; I 2 (s) + 3Cl 2 (g)  I 2 Cl 6 (s) ; (dimeric form)

20. Reactions of Interhalogen Compounds ClF 3 & BrF 3 – fluoridating agents 1.2B 2 O 3 (s) + 2BrF 3 (l)  4BF 3 (g) + Br 2 (l) + 3 O 2 (g) 2.P 4 (s) + 5ClF 3 (g)  4PF 3 (g) + Cl 2 (g) + 3ClF (g) Reaction with water is explosive: 1.ClF 3 (g) + 2H 2 O (l)  HClO 2 (aq) + 3HF (aq) ; 2.BrF 5 (l) + 3H 2 O (l)  HBrO 3 (aq) + 5HF (aq) ;

21. Chemistry of Chlorine Most important halogen Laboratory preparation from MnO 2, NaCl and H 2 SO 4 : 2NaCl (s) + MnO 2 (s) + 2H 2 SO 4 (l)  Cl 2 (g) + MnSO 4 (s) + Na 2 SO 4 (s) + 2H 2 O (l) Industrial production: Chlorine is a by-product in the electrolysis of NaCl, MgCl 2, CaCl 2, ScCl 3, etc.

22. Major Uses of Chlorine Production of chlorinated organic compounds; Production of hydrochloric acid; Production of bleach solution and bleach powder; Treatment of municipal water.

23. Production of Bleach Solution 1.Cl 2 (g) + 2NaOH (aq)  NaOCl (aq) + NaCl (aq) + H 2 O (l)

24. Production of Bleach Powder 2Cl 2 (g) + 2Ca(OH) (aq)  Ca(OCl) 2 (s) + CaCl 2 (aq) + 2H 2 O (l)

25. Production of Other Oxidizing Agents 3Cl 2 (g) + 6NaOH (aq)  NaClO 3 (aq) + 3NaCl (aq) + 3H 2 O (l) 2NaClO 3 (s) + SO 2 (g) + H 2 SO 4 (aq)  2ClO 2 (g) + 2NaHSO 4 (aq)

26. Oxides and Oxyacids of Chlorine Oxides of chlorine and its oxidation number (in parenthesis): Cl 2 O (+1), Cl 2 O 3 (+3), ClO 2 (+4; unstable), Cl 2 O 5 (+5), Cl 2 O 7 (+7; highest possible) Chlorine oxyacids in increasing acid strength HOCl < HClO 2 < HClO 3 < HClO 4 ; HClO 4 is a strong oxidization agent

27. Important Compounds of Chlorine NaCl – for electrolyte balance NaOCl – household bleach solution Ca(OCl) 2 – bleach for water & sewage treatment ClO 2 – bleach for paper production NaClO 3 – production of industrial bleach (ClO 2 ) KClO 3 – oxidizer in fireworks and matches NaClO 4 – production of HClO 4 and NH 4 ClO 4 NH 4 ClO 4 – oxidizer in booster rocket fuel

28. Noble Gases He and Ne form no compounds. Kr and Xe have been observed to form compounds with oxygen and fluorine: Xe (g) + 2F 2 (g)  XeF 4 (s) Xe (g) + 3F 2 (g)  XeF 6 (s) XeF 6 (s) + 3H 2 O (l)  XeO 3 (aq) + 6HF (aq) XeF 6 (s) + 2H 2 O (l)  XeO 2 F 2 (aq) + 4HF (aq) XeF 6 (s) + H 2 O (l)  XeOF 4 (aq) + 2HF (aq)

29. Selected Properties

30. Concept Check Which of the following groups is the most reactive? a) Group 1A Elements b) Group 5A Elements c) Group 6A Elements d) Group 8A Elements

31. Concept Check Which of the following groups does not contain at least one element that forms compounds with oxygen? a) Group 4A Elements b) Group 5A Elements c) Group 6A Elements d) Group 7A Elements e) All of these groups contain at least one element that forms compounds with oxygen.

32. Exercise #10a Draw Lewis structures for the following molecules, propose hybridization, and predict whether each molecule is polar or nonpolar. 1.BF 3 2.NF 3 3.ClF 3 4.SiF 4 5.SF 4 6.XeF 4