1. Periodic Trends (a.k.a. “Periodicity”)
Properties of atoms that can be predicted by patterns on the periodic table.

3. Atomic Radius the SIZE of an atom from nucleus to outer energy level
More energy levels (bottom) = larger radius or size
Atoms with more p+ (right) are smaller because positive charge attracts e- more

4. Atomic Size Increase

5. Metallic Character
Metals
Nonmetals

6. Metallic Character
Metallic character means an atom tends to give up electrons easily
Atoms with fewer valence e- (left) want to lose them to get an octet
Larger atoms (bottom) lose e- more easily because p+ in nucleus are farther away.

7. Metallic Character Trend

8. Electronegativity
The ability of an atom to attract and hold an extra electron (how “greedy” atom is for e-)
Atoms that are small (top) can attract e- easier since nucleus is closer
Atoms with ALMOST full valence shells (right) really want more e- to be stable/happy

9. Electronegativity Trend

10. Ionization Energy
The energy needed to remove an electron from an atom (a.k.a. to make the atom an ion)
More electronegative = harder to remove an electron = higher ionization energy

11. Ionization Energy

12. Reactivity Determined by position on the table:
Metals: most metallic character
Non-metals: most electronegativity

13. Review Questions: How do energy levels determine size?
Which element probably has the most metallic character?
Which is the largest?
Why does it take more energy to remove an electron from F than it does to remove an e- from Cs?
Pair up the trends according to their similarity (look at arrows!).