1. Launch: 10/12 1. What is the main
difference?
Unit #2 Exam Data:
2. What is the biggest
reason for the
difference?
Quiz #4 Data: Our Goal: 80%
Our Score: 79.29%

2. Launch: 10/12 1. What is the main
Unit #2 Exam Data: difference?
2. What is the biggest
reason for the
difference?
Quiz #4 Data: Our Goal: 80%
Our Score: 79.29%

3. Launch: 10/12 1. What is the main
difference?
Unit #2 Exam Data:
2. What is the biggest
reason for the
difference?
Quiz # 4 Data: Our Goal: 80%
Our Score: 79.17%

4. Launch: 10/12 1. What is the main
difference?
Unit #2 Exam Data:
2. What is the biggest
reason for the
difference?
Quiz # 4 Data: Our Goal: 80%
Our Score: 79.00%

5. Mid-Term Exam Info
 Cumulative exam
 Unit #1: Atomic Structure
 Unit #2: The Periodic Table
 Unit #3: Nuclear Processes
 Opportunity to change your grade
 We don’t have much time!
 If you don’t understand something, ask!
 No copying

6. What is the trend in
atomic radius?
Mr. Heffner
10/12/09

7. Review: Period vs. Group
 Period = row (left to right)
 Group = column (top to bottom)

8. Atomic Radius
 Atomic radius is…
 the size of an atom.
0
0 0
0
 big radius = big atom

9. Atomic Radius
 The trend:
1. Atomic radius decreases across a period (LR)
2. Atomic radius increases down a group (Top  Bottom)
Decreases
Increases

10. Example
Which has a smaller atomic radius,
fluorine (F) or nitrogen (N)?
 Step #1: Find the elements

11. Example
Which has a smaller atomic radius,
fluorine (F) or nitrogen (N)?
 Step #2: Look at the keyword
Which has a smaller atomic radius,
fluorine (F) or nitrogen (N)?

12. Example
Which has a smaller atomic radius,
fluorine (F) or nitrogen (N)?
 Step #3: Identify which is closest to He

13. Example
Which has a larger atomic radius,
sodium (Na) or potassium (K)?
 Step #1: Find the elements

14. Example
Which has a larger atomic radius,
sodium (Na) or potassium (K)?
 Step #2: Look at the keyword
Which has a larger atomic radius,
sodium (Na) or potassium (K)?

15. Example
Which has a larger atomic radius,
sodium (Na) or potassium (K)?
 Step #3: Identify which is closest to Fr

16. Practice Questions
 Review Worksheet #1
 Use the 3-step method!

17. Atomic Radius
 The trend:
1. Atomic radius decreases across a period (LR)
2. Atomic radius increases down a group (Top  Bottom)
Decreases
Increases

18. Homework
 Review your notes
 Finish Review Worksheet #1
 Make a problem from scratch like question 6 or 7
on the worksheet. Solve it!