1. Opposites attract

2. attract

3. repel

4. In a many-electron atom, each electron feels both the attraction to the protons in the nucleus and the repulsion from other electrons Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

5. Effective nuclear charge

6. In a many-electron atom, each electron feels both the attraction to the protons in the nucleus and the repulsion from other electrons Force of attraction increases as nuclear charge (# of protons) increases Force of attraction decreases as the electron goes farther from the nucleus Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

7. In effect, the charge felt by an electron is less than the full nuclear charge Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

8. In effect, the charge felt by an electron is less than the full nuclear charge The effective nuclear charge (Z eff ) is the nuclear charge that is actually felt by an electron An electron is shielded from the full charge of the proton –greatly by the inner electrons –only slightly by the other electrons in the same principal quantum number (n) –not at all by outer electrons Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

9. The effective nuclear charge and electron configuration are key in understanding the periodic trends Atomic radius Ionic radius –neutral vs. charged –isoelectronic series Ionization energy –one atom vs. another –same atom Electron affinity Chemical properties Physical properties

10. Atomic radius

11. Atomic radius is ½ the distance between the two nuclei in two adjacent atoms Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill.

12. *Radii in pm

13. Z eff dominates number of protons increases electrons are added to the same n, so shielding by inner electrons does not change while shielding by electrons belonging to the same n is poor Left to right: decreasing atomic radius Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill. Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill. Decreasing atomic radius

14. n dominates going down the group, each member has one more level of inner electrons that shield the outer electrons very effectively Top to bottom: increasing atomic radius Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill. Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

15. Ionic radius: Neutral vs. charged

17. If the atom forms a cation, its radius decreases same number of protons less electrons electron-electron repulsion is reduced the electron cloud becomes smaller Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill.

18. If the atom forms an anion, its radius increases same number of protons more electrons electron-electron repulsion is enhanced the electron cloud becomes bigger Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill.

19. Ionic radius: Isoelectronic series

20. Ions having the same electron configuration and same number of electrons are said to be isoelectronic Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill. IonElectron Configuration Number of Electrons F-F- [Ne]10 O 2- [Ne]10 N 3- [Ne]10

22. Left to right: decreasing ionic radius same number of electrons increasing number of protons stronger attraction between the protons and the electrons

23. Ionization energy: One atom vs. another

24. Ionization energy (IE) is the minimum energy required to remove an electron from a gaseous atom Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill. energy + X (g)  X + (g) + e - The higher the IE, the more difficult it is to remove the electron

25. Brown,, E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8 th ed. Phils: Pearson Education Asia Pte. Ltd.

26. Left to right: increasing ionization energy Z eff dominates number of protons increases same n stronger attraction between the protons and the electrons harder to remove an electron Increasing ionization energy Brown,, E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. Phils: Pearson Education Asia Pte. Ltd. Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill.

27. Top to bottom: decreasing ionization energy n dominates there are more electrons in between the protons and the outer electrons weaker attraction easier to remove an electron Decreasing ionization energy Brown,, E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. Phils: Pearson Education Asia Pte. Ltd. Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill.

28. Ionization energy: Same atom

29. If more than one electron could be removed from the same atom, there will be different IE values X (g)  X + (g) + e - IE 1 X + (g)  X 2+ (g) + e - IE 2 X 2+ (g)  X 3+ (g) + e - IE 3 Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill....

30. Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

31. For the same atom, IE 1 < IE 2 <IE 3 same number of protons, less electrons same nuclear charge, less electron- electron repulsion greater attraction between the proton and the remaining electrons harder to remove another electron Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill.

32. There is a dramatic increase in IE when an electron is removed from an atom/ion with a noble gas configuration the noble gas configuration is stable removing another electron from it will result in instability Chang, R. 2002. Chemistry 7 th ed. Singapore: McGraw-Hill.

33. Electron affinity

34. Electron affinity (EA) is the energy change accompanying the addition of electrons to atoms or ions The more negative the electron affinity, the greater the tendency to accept an electron Note: different books may use different sign conventions X (g) + e -  X - (g) energy gained (+) or released (-) *usually released Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

35. *Energies in kJ/mol

36. Left to right: increasingelectron affinity Z eff dominates size decreases stronger attraction between the protons and the added electron Increasing electron affinity Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

37. Top to bottom: decreasing (esp. for Group 1A) For Group 1A, –the nucleus is farther away from an electron being added –weaker attraction between the protons and the added electron Decreasing electron affinity Silberberg, M. 2010. Principles of General Chemistry. 2 nd ed. New York: McGraw-Hill.

38. Factors other than Z eff and atomic size affect electron affinities, so trends are not as regular as those for the other properties