1. Chapter 20 The Representative Elements

2. Section 20.1 A Survey of the Representative Elements Return to TOC Copyright © Cengage Learning. All rights reserved 2 The Atomic Radii of Some Representative Elements (in Picometers)

3. Section 20.2 Atomic MassesThe Group 1A Elements Return to TOC Copyright © Cengage Learning. All rights reserved 3 Reaction of Group 1A Metals Reactions with water: 2Li (s) + 2H 2 O → 2LiOH (aq) + H 2 2Na (s) + 2H 2 O → 2NaOH (aq) + H 2 2K (s) + 2H 2 O → 2KOH (aq) + H 2 2Rb (s) + 2H 2 O → 2RbOH (aq) + H 2 2Cs (s) 2H 2 O → 2CsOH (aq) + H 2 2X (s) 2H 2 O → 2XOH (aq) + H 2

4. Section 20.2 Atomic MassesThe Group 1A Elements Return to TOC Copyright © Cengage Learning. All rights reserved 4 Reaction of Group 1A Metals In the presence of excess oxygen: 4Li + O 2 → 2Li 2 O 2Na + O 2 → Na 2 O 2 K + O 2 → KO 2 Rb + O 2 → RbO 2 Cs + O 2 → CsO 2 In the presence of a halogen: 2Na + Cl 2 → 2NaCl

5. Section 20.2 Atomic MassesThe Group 1A Elements Return to TOC Reactions of Group 1A Oxides In water… oxides form hydroxides Li 2 O + H 2 O → 2LiOH peroxides form hydroxides and hydrogen peroxide Na 2 O 2 + 2H 2 O → 2NaOH + H 2 O 2 superoxides form hydroxides and hydrogen peroxide and oxygen 2KO 2 + 2H 2 O → 2KOH + 2H 2 O 2 + O 2 Copyright © Cengage Learning. All rights reserved 5

6. Section 20.2 Atomic MassesThe Group 1A Elements Return to TOC Reactions of Group 1A Oxides continued… In dilute acid, instead of a base forming, an acid-base reaction occurs and forms a salt and the other products from reaction with water. Li 2 O + HCl → LiCl + H 2 O Na 2 O 2 + HCl → NaCl + H 2 O 2 KO 2 + HCl → KCl + H 2 O 2 + O 2 Copyright © Cengage Learning. All rights reserved 6

7. Section 20.3 The MoleThe Chemistry of Hydrogen Return to TOC Copyright © Cengage Learning. All rights reserved 7 Hydrides Binary compounds containing hydrogen:  Ionic hydrides: hydrogen + the most active metals (group I and group II) (eg; LiH, CaH 2 )  Covalent hydrides: hydrogen + other nonmetals (eg; H 2 O, CH 4, NH 3 )  Metallic (interstitial) hydrides: transition metal crystals treated with H 2 gas

8. Section 20.3 The MoleThe Chemistry of Hydrogen Return to TOC Copyright © Cengage Learning. All rights reserved 8 Exercise Predict the products formed by the following reactants: LiH(s) + H 2 O(l) → H 2 (g) + LiOH(aq) Ionic hydrides react with water to produce hydrogen gas and a hydroxide.

9. Section 20.3 The MoleThe Chemistry of Hydrogen Return to TOC Copyright © Cengage Learning. All rights reserved 9 Reaction of Group 2A Metals Reactions with water: Be has no rxn with water Mg (s) + H 2 O (l) → Mg(OH) 2 (s) + H 2 Ca (s) + 2H 2 O (l) → Ca(OH) 2 (aq) + H 2 Sr (s) + 2H 2 O (l) → Sr(OH) 2 (aq) + H 2 More reactive with water as you go down the group X (s) + 2H 2 O → X(OH) 2 (aq) + H 2

10. Section 20.4 The Group 2A Elements Return to TOC Reactions of Group 2A Metals Copyright © Cengage Learning. All rights reserved 10

11. Section 20.5 The Group 3A Elements Return to TOC Copyright © Cengage Learning. All rights reserved 11 Group 3A elements generally show the increase in metallic character in going down the group that is characteristic of the representative elements. B, Al, Ga, In, Tl Notice that Boron is a nonmetal!

12. Section 20.5 The Group 3A Elements Return to TOC Copyright © Cengage Learning. All rights reserved 12 Some Important Reactions

13. Section 20.5 The Group 3A Elements Return to TOC Complex ion formation of Al Al(H 2 O) 6 3+ ↔ Al(OH)(H 2 O) 5 2+ + H + Salt that produces an acidic solution Lewis acid base reaction Copyright © Cengage Learning. All rights reserved 13 What species is acting as the Lewis acid? Lewis base? Al OH -

14. Section 20.6 The Group 4A Elements Return to TOC Copyright © Cengage Learning. All rights reserved 14 Contains two of the most important elements on earth: carbon and silicon. Can form four covalent bonds to nonmetals.  CH 4, SiF 4, GeBr 4

15. Section 20.8 The Chemistry of Nitrogen Return to TOC Copyright © Cengage Learning. All rights reserved 15 Exhibits varied chemical properties. N, P, As, Sb, Bi Compounds of N –NH 3 NF 3 only 3 bonds total Compounds of P –PH 3, PF 3, but also PF 6 How???

16. Section 20.8 The Chemistry of Nitrogen Return to TOC Copyright © Cengage Learning. All rights reserved 16 Nitrogen Fixation The process of transforming N 2 to other nitrogen–containing compounds. The Haber Process: N 2 (g) + 3H 2 (g) → 2NH 3 (g) ∆H o = -92 kJ

17. Section 20.8 The Chemistry of Nitrogen Return to TOC Copyright © Cengage Learning. All rights reserved 17 Nitrogen Oxides Nitrogen in its oxides has oxidation states from +1 to +5.  In other compounds, nitrogen could have oxidation states of -1 to -3. CompoundOxidation State of N N 2 O+1 NO+2 N 2 O 3 +3 NO 2 +4 HNO 3 +5

18. Section 20.8 The Chemistry of Nitrogen Return to TOC Copyright © Cengage Learning. All rights reserved 18 Nitrogen Oxyacids Nitric acid, HNO 3 (strong acid) Nitrous acid, HNO 2 (weak acid)

19. Section 20.8 The Chemistry of Nitrogen Return to TOC Copyright © Cengage Learning. All rights reserved 19 The Ostwald Process

20. Section 20.9 The Chemistry of Phosphorus Return to TOC Copyright © Cengage Learning. All rights reserved 20 Phosphorus Oxyacids P 4 O 10 + H 2 O → H 3 PO 4 (phosphoric acid) P 4 O 6 + H 2 O → H 3 PO 3 (phosphorous acid) Hypophosphorous acid, H 3 PO 2

21. Section 20.12 The Chemistry of Sulfur Return to TOC Copyright © Cengage Learning. All rights reserved 21 Sulfur Oxide Reactions 2SO 2 (g) + O 2 (g) → 2SO 3 (g) SO 2 (g) + H 2 O(l) → H 2 SO 3 (aq) (sulfurous acid) SO 3 (g) + H 2 O(l) → H 2 SO 4 (aq) (sulfuric acid)

22. Section 20.13 The Group 7A Elements Return to TOC Copyright © Cengage Learning. All rights reserved 22 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 (strong acids)

23. Section 20.13 The Group 7A Elements Return to TOC Copyright © Cengage Learning. All rights reserved 23 Halogen Oxyacids and Oxyanions All halogens except fluorine combine with various numbers of oxygen atoms to form a series of oxyacids Notice the varying oxidation states of the halogen.

24. Section 20.13 The Group 7A Elements Return to TOC Halogen Oxyacids and Oxyanions The strengths of these acids vary in direct proportion to the number of oxygen atoms attached to the halogen, with the acid strength increasing as more oxygens are added. Copyright © Cengage Learning. All rights reserved 24

25. Section 20.14 The Group 8A Elements Return to TOC Copyright © Cengage Learning. All rights reserved 25 Noble Gases He and Ne form no compounds. Kr and Xe have been observed to form chemical compounds: Xe(g) + 2F 2 (g) → XeF 4 (s) [6 atm, 400 o C] XeF 6 (s) + 3H 2 O(l) → XeO 3 (aq) + 6HF(aq)

26. Section 20.14 The Group 8A Elements Return to TOC Of course there are more reaction types to consider Refer to Packet from Winter Break for more reaction types (Ch 9, 10, 13 Chemical Equations Handouts) Copyright © Cengage Learning. All rights reserved 26