1. Do Now (5 min) 1. How does atomic radius change as you move across a period? 2. How does atomic radius change as you move down a group?

2. Do Now Discussion 1. How does atomic radius change as you move across a period? Decreases 1. How does atomic radius change as you move down a group? Increases

3. 12/7/09 1. Recap from yesterday 2. Cornell Notes 3. Practice

4. Periodic Trends A predictable change in how an element behaves either down a group or across a period on the periodic table Trends we will study: Atomic radius Electronegativity Reactivity Ionic radius Ionization energy

5. Atomic Radius Measure of the size of an atom Decreases across a period  Increasing positive charge in the nucleus pulls electrons closer Increases down a group  Increasing number of non-valence electrons shields outer electrons from being pulled toward the nucleus

6. Example: Which has a LARGER atomic radius: Yttrium or Fluorine? YTTRIUM

7. Electronegativity The ability of an atom to attract electrons in a chemical bond  Increases across a period  Increases up a group  NOTE: noble gases have no electronegativity value!

8. Example: Which element is MORE electronegative: Indium or Phosphorus? PHOSPHORUS

9. Reactivity How easily an element reacts or combines with other elements to form compounds. Metals: increases down a group and to the left Non-Metals: increases down a group and to the right (with exception to the noble gases)

10. Example: Which metal has a higher reactivity: Cesium or Cobalt? Cesium

11. Tic-Tac-Toe Practice 1. Select ONE card 2. Answer the questions on your board in the correct spot 3. Have your card checked by Ms. Akagi 4. Select a new card 5. Goal: Get THREE in a row of THREE different colors.