1. Periodic Trends

2. characteristicsdescribe characteristics of elements across periods and among families absoluteare not absolute – represent general trends shielding effectare based largely on the “shielding effect”

3. Shielding Effect protectioncore lessensvalenceThe protection provided by the inner core electrons which lessens the nucleus’s pull on the outer valence electrons Across a perioddoes not play outermostAcross a period, it does not play a significant role (all elements in a period have valence electrons in the same outermost energy level). Down a family significant core valence awayDown a family, it plays an increasingly more significant role (each family member has an additional layer of core electrons, moving the valence electrons further away from the nucleus).

4. Atomic Radius Definition Definition: half the distance between the nuclei of like atoms in a solid Trend Trend: decreases from left to right and increases from top to bottom

6. Electronegativity Definition Definition: measure of attraction an atom has for a unshared pair of electrons Trend Trend: increases from left to right and decreases from top to bottom (excluding noble gases)

8. Ionization Energy Definition Definition: amount of energy needed to release an electron from a gaseous atom Trend Trend: increases from left to right and decreases from top to bottom

10. Reactivity Metals: Metals: are more reactive with small ionization energies, small electronegativity values, and large atomic radii -Trend: down and to the left Francium: most reactive metal Nonmetals: Nonmetals: are more reactive with large ionization energies, large electronegativity values, and small atomic radii -Trend: up and to the right (excluding noble gases) Fluorine: most reactive nonmetal

11. Reactivity

12. Periodic Trends Examples Which of the following is the largest atom: Li, Rb, or Fr? Fr

13. Periodic Trends Examples Rank the following atoms by decreasing atomic radius: Cs, Pb, At. Cs  Pb  At

14. Periodic Trends Examples Which of the following has the greatest ionization energy: Rb, Sr, I, or O? O

15. Periodic Trends Examples Rank the following in order of increasing ionization energy: Cs, Bi, Rn, F. Cs  Bi  Rn  F

16. Periodic Trends Examples Which of the following has the greatest electronegativity: Li, Cs, or K? Li

17. Periodic Trends Examples Rank the following in order of decreasing electronegativity: Fr, As, F. F  As  Fr

18. Periodic Trends Examples Which metal is more reactive, Cs or Ca? Cs

19. Periodic Trends Examples Which nonmetal is more reactive, C or N? N