1. Periodic Trends Pages 28 and 29 of your Workbook

2. In the periodic table, vertical columns are called groups or families…

3. … while the horizontal rows are called periods.

4. Atomic Radius (AR) Make a QUICK sketch of this picture in the box. in the box.

5. Atomic Radius Across a period, atomic radius decreases. Reason: More protons pull on electrons which are in orbitals with similar energies.

6. Atomic Radius

7. Down a group, atomic radius increases. Reason: Elements have electrons in higher energy orbitals, which are farther from the nucleus.

8. The smallest radius is ______ while the largest radius is ________. The smallest radius is ______ while the largest radius is ________. Atomic Radius helium cesium(francium)

9. Rank the following from largest AR to smallest. 1) Br, Se, Ca 1) Br, Se, Ca Answer: Ca > Se > Br Answer: Ca > Se > Br Reason: Across a period radius ↓ Reason: Across a period radius ↓ 2) Be, Ca, Ba 2) Be, Ca, Ba Answer: Ba > Ca > Be Answer: Ba > Ca > Be Reason: Down a family, radius ↑ Reason: Down a family, radius ↑

10. Atomic Radius Atomic Radius Animation Atomic Radius Animation

11. Practice: 1. Arrange the following elements in order of increasing AR: Pb, Ba, Cs, At ___<___<___<___ 2. Arrange the following elements in order of decreasing AR: Be, Ba, Mg, Ra ___>___>___>___ At Pb Ba Cs Ra Ba Mg Be

12. Ion vs. Atom Size

13. Positive Ions Atom Size: Ion Size:

14. Positive Ions Positive ions are smaller than neutral atoms. Reason: There are the same number of protons pulling on fewer electrons.

15. Negative Ions Atom Size: Ion Size:

16. Negative Ions Negative ions are larger than neutral atoms. Reason: There are the same number of protons pulling on more electrons. ( More repulsion between electrons in electron cloud)

17. Practice:, H +1, and H -1 from largest to smallest AR: 1. Rank H, H +1, and H -1 from largest to smallest AR: H -1 > H > H +1 H -1 > H > H +1 2. Which is larger: F -1 Ca or Ca +2, F or F -1 ? Ca > Ca +2 and F -1 > F

18. Ionic Radii Same trend as atoms, only with negative ions (anions) larger than positive ions (cations).

19. Practice: 1.Rank the following ions from smallest to largest: Cl -1, I -1, F -1 : F -1 < Cl -1 < I -1 2. Rank the following ions from smallest to largest: Li +1, Cs +1, Na +1 : Li +1 < Na +1 < Cs +1 3. Rank the following ions from smallest to largest: O -2, O -1, O : O < O -1 < O -2

20. Isoelectronic Series An isoelectronic series contains atoms/ions with the same number of electrons. For example, Cl -1, Ar, and K +1 all have ______ electrons. When comparing the atomic radii in such a series, the key is to look at the number protons for each: The greater the number of protons pulling on the same number of electrons, the ______________ the radius. _______ > _______ > _______ Cl -1 Ar K +1 Cl -1 Ar K +1 18 smaller

21. Practice: The two cations Na +1 and Al +3 are isoelectronic with what noble gas? ______. The ions both have ______ electrons, but Na has 11 protons and Al has 13 protons. Which ion will have the smaller AR and why? Ne Ne Al +3 will have a smaller AR because it has more protons. 10 10

22. Isoelectronic Series Animation

23. Ionization Energy

24. Ionization Energy (IE) ~ the energy required to remove an e - Across a period, ionization energy increases. Reason: Smaller atoms hold electrons more tightly (e - are closer to the nucleus). Check yourself! Which atoms are the smallest? Which atoms will have the highest IE’s?

25. Ionization Energy (IE) ~ the energy required to remove an e - Down a group, ionization energy decreases. Reason: Valence e - in larger atoms are farther from the nucleus. (e - are not as attracted to nucleus). Check yourself! Which atoms are the smallest? Which atoms will have the highest IE’s?

26. Practice 1.Arrange the following elements in order of increasing IE: Pb, Ba, Cs, At Cs < Ba < Pb < At 2. Arrange the following elements in order of decreasing IE: Al, Na, S, Cl Na < Al < S < Cl