Trends in the periodic table:

1. Trendsin the periodic table: ATOMIC RADIUS IONIZATION ENERGYELECTRON AFFINITYELECTRONEGATIVITY

2. Can Studying Chemistry Be Trendy? • As you look at the periodic table and focus in on the elements and their characteristics, you can see there are noticeable patterns (trends) that go across a period (horizontal row) on the periodic table. • These quantitative characteristics that follow distinct patterns across the periodic table are called periodic trends. • Remember…Mendeleev didn’t get all the fame and fortune for nothing – he was crazy smart! • The periodic trends that we will be studying are: • Atomic Radius • Ionization Energy • Electron Affinity • Electronegativity

3. Periodic trends • Density • In the second energy level (n=2), if we look from the left of the chart to the right we first see: • Li (metal), then Be (metal), B (metalloid), C (nonmetal), N (nonmetal), O, F, and Ne (all nonmetals). • This pattern holds true for every energy level. As you read the periodic table from left to right, first are the metals, followed by the metalloids, and finally the nonmetals. • The densities of the elements vary in a regular way when plotted against atomic numbers of the elements. • Metals have the highest density and nonmetals have the lowest density.

4. FACTORS AFFECTING PERIODIC TRENDS Influenced by Number of Energy Levels (Size) The distance between the nucleus and the outer electrons Higher energy levels are further away from the nucleus Electrons in these levels are affected less by the electrostatic pull towards the nucleus. Shielding Effect Inner shell electrons have the ability to block the nuclear pull (charge on p+) on the outer electrons This mainly effects group trends. Nuclear Charge The number of protons in the nucleus Higher charge pulls electrons in closer towards the nucleus This greatly effects period trends because shielding effect is not an issue across a period. Electron Configuration Filled and Half-filled sublevels are more stable, thus causing exceptions to some trends

5. Shielding • The electron on the outside energy level has to look through all the other energy levels to see the nucleus

6. Shielding effect Lithium – 3Li Rubidium – 37Rb

7. Atomic Size – radii of atoms • It is difficult to measure the radius of an atom simply because the electron is in constant random motion about the nucleus. • The electron cloud doesn’t have a definite edge. • Scientists took a diatomic molecule and measured the distance between the two nuclei. • Cutting the number in half gives the approximate radius of each of the atoms.

8. Covalent Radius of Iodine

9. Determining the Atomic Radius of a Nonmetal (Carbon)

11. Atomic radii in picometers (10-12 m)

12. Atomic radii in picometers (10-12 m)

13. Atomic radii in picometers (10-12 m)

14. Atomic radii in picometers (10-12 m)

20. 37

21. 37 50

22. 37 50 140

23. 37 50 140 90

24. 37 50 80 140 90

25. 37 50 90 80 77 140

26. 37 50 140 90 80 77 71

27. 37 50 140 90 80 77 71 66

28. 37 50 140 90 80 77 71 66 64

29. 37 50 140 90 80 77 71 66 64 70

30. 37 50 90 80 77 71 66 64 70 140 157

31. 37 50 90 140 80 77 71 66 64 70 157 136

32. 37 50 90 80 77 71 66 64 70 140 157 136 143

33. 37 50 140 80 77 71 66 64 70 90 157 136 143 118

34. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109

35. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103

36. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91

37. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94

38. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196

39. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

40. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

41. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

42. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

43. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

44. 37 50 140 90 80 77 71 66 64 70 157 136 143 118 109 103 91 94 196 174

45. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

46. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

47. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

48. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

49. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174

50. 37 50 140 80 77 71 66 64 70 90 157 136 143 118 109 103 91 94 196 174