1. PERIODICITY AND ELECTRON CONFIGURATIONS

3. Effective Nuclear Charge Electron cloud for 1s electrons Figure 8.6

7. Atomic Radii Figure 8.9

8. Trends in Atomic Size See Figures 8.9 & 8.10

9. Ion Sizes Does the size go up or down when losing an electron to form a cation? Idea Check! What do you think?

11. Ion Sizes Does the size go up or down when gaining an electron to form an anion? Idea Check!

13. Trends in Ion Sizes Figure 8.13

14. Redox Reactions Why do metals lose electrons in their reactions? Why does Mg form Mg 2+ ions and not Mg 3+ ? Why do nonmetals take on electrons?

15. Ionization Energy See Screen 8.12 IE = energy required to remove an electron from an atom in the gas phase. Mg (g) + 738 kJ ---> Mg + (g) + e-

16. Mg (g) + 735 kJ ---> Mg + (g) + e- Mg + (g) + 1451 kJ ---> Mg 2+ (g) + e- Mg 2+ (g) + 7733 kJ ---> Mg 3+ (g) + e- Energy cost is very high to dip into a shell of lower n. This is why ox. no. = Group no. Ionization Energy See Screen 8.12

17. Trends in Ionization Energy

20. Electron Affinity A few elements GAIN electrons to form anions. Electron affinity is the energy change when an electron is added: A(g) + e- ---> A - (g) E.A. = ∆E

21. Electron Affinity of Oxygen ∆ E is EXO thermic because O has an affinity for an e-. EA = - 141 kJ [He]       O atom + electron O [He]       - ion

22. Electron Affinity of Nitrogen ∆ E is zero for N - due to electron-electron repulsions. EA = 0 kJ [He]     N atom  [He]     N - ion  + electron

24. Trends in Electron Affinity