1. Chapter 19(a) The Representative Elements: Groups 1A Through 4A

2. Copyright © Houghton Mifflin Company. All rights reserved.19a–2 Figure 19.1: The periodic table.

3. Figure 19.2: The atomic radii of some atoms in picometers.

4. Figure 19.3: The structure of quartz, which has the empirical formula SiO 2.

5. Copyright © Houghton Mifflin Company. All rights reserved.19a–5

6. Copyright © Houghton Mifflin Company. All rights reserved.19a–6

7. Copyright © Houghton Mifflin Company. All rights reserved.19a–7

8. Copyright © Houghton Mifflin Company. All rights reserved.19a–8 Figure 19.4: Lepidolite is composed mainly of lithium, aluminum, silicon, and oxygen, but it also contains significant amounts of rubidium and cesium.

9. Copyright © Houghton Mifflin Company. All rights reserved.19a–9

10. Copyright © Houghton Mifflin Company. All rights reserved.19a–10

11. Copyright © Houghton Mifflin Company. All rights reserved.19a–11

12. Copyright © Houghton Mifflin Company. All rights reserved.19a–12 (left) Hydrogen gas being used to blow soap bubbles. (right) As the bubbles float upward, they are lighted using a candle on a long pole. The orange flame is due to the heat from the reaction of hydrogen with the oxygen in the air that excites sodium ions in the soap solution.

13. Copyright © Houghton Mifflin Company. All rights reserved.19a–13 Figure 19.5: The structure of ice, showing the hydrogen bonding.

14. Chapter 19(b) The Representative Elements: Groups 1A Through 4A (cont’d)

15. Copyright © Houghton Mifflin Company. All rights reserved.19a–15

16. Copyright © Houghton Mifflin Company. All rights reserved.19a–16 Calcium metal reacting with water to form bubbles of hydrogen gas.

17. Figure 19.6: (a) Solid BeCl 2 can be visualized as being formed from many BeCl 2 molecules, where lone pairs on the chlorine atoms are used to bond to the beryllium atoms in adjacent BeCl 2 molecules. (b) The extended structure of solid BeCl 2. (c) The ball-and-stick model of the extended structure.

18. Copyright © Houghton Mifflin Company. All rights reserved.19a–18

19. Figure 19.7: (a) A schematic representation of a typical cation- exchange resin. (b) and (c) When hard water is passed over the cation- exchange resin, the Ca2 + and Mg2 + bind to the resin.

20. Copyright © Houghton Mifflin Company. All rights reserved.19a–20

21. Gallium metal has such a low melting point (30ºC) that it melts from the heat of a hand.

22. Copyright © Houghton Mifflin Company. All rights reserved.19a–22 Figure 19.8: (a) The structure of B 2 H 6 with its two three- center B—H—B bridging bonds and four "normal" B—H bonds. (b) The structure of B 5 H 9. There are five "normal" B—H bonds to terminal hydrogens and four three-center bridging bonds around the base.

23. Copyright © Houghton Mifflin Company. All rights reserved.19a–23

24. Copyright © Houghton Mifflin Company. All rights reserved.19a–24

25. Copyright © Houghton Mifflin Company. All rights reserved.19a–25

26. Copyright © Houghton Mifflin Company. All rights reserved.19a–26 Lead (II) oxide, known as litharge.

27. Copyright © Houghton Mifflin Company. All rights reserved.19a–27