1. Chem-To-Go Lesson 11 Unit 3 ATOMIC RADIUS & IONIC RADIUS

2. TRENDS Trend = a repeating pattern Periodic Trend = a repeating pattern on the periodic table

3. ATOMIC RADIUS Definition: ½ the distance between the nuclei of two identical touching atoms

4. ATOMIC RADIUS Period trend: [row pattern]; atomic radius DECREASES from left to right across a row Group trend: [column pattern]; atomic radius DECREASES from bottom to top of a column WHY? Radius decreases across a period because the nucleus is gaining more protons to become larger and more strongly positive. The electron cloud is drawn in by forces of attraction. Radius decreases up a group because there are fewer energy levels at the top of the periodic table. PERIOD TREND GROUP TREND

5. ATOMIC RADIUS Memory Tool SAMPLE MULTIPLE CHOICE: 1. Which of the following atoms will has the smallest radius? a. Tinb. Strontium c. Selenium d. Arsenic Use a periodic table! Find all of the elements. Apply the trend.

6. ATOMIC RADIUS Memory Tool SAMPLE MULTIPLE CHOICE: 2. Which of the following atoms will has a larger radius than calcium? a.Aluminum b. Copper c. Potassiumd. None Use a periodic table! Find all of the elements. Apply the trend.

7. IONIC RADIUS Definition: size of the ion; usually compared to the size of its neutral atom

8. CATION RADIUSANION RADIUS IONIC RADIUS Cations form by losing electrons. As electrons are lost, the ion becomes smaller. Anions form by gaining electrons. As electrons are gained, the ion becomes larger.