1. Review – Electron Energy Levels
The atom contains energy levels (Bohr called them “shells”) .
The first energy level holds 2 electrons.
The second energy level holds 8 e-
The third energy level holds 8 e-

2. Example: Helium How many protons: 2 How many neutrons:
How many electrons:
Electrons in 1st energy level:
Electrons in 2nd energy level:
Electrons in 3rd energy level: 2 2 2 2

3. Example: Phosphorus How many protons: 15 How many neutrons:
How many electrons:
Electrons in 1st energy level:
Electrons in 2nd energy level:
Electrons in 3rd energy level: 15 16 15 2 8 5

4. Be Electron Dot Diagram Looks only at the valence electrons.
Dots represent electrons.
Ex: Beryllium has 2 valence electrons Be

5. Example:
Oxygen: How many valence electrons: O 6

6. Example:
Sodium: How many valence electrons: Na 1

7. Example:
Florine: How many valence electrons: F 7

8. What do atoms want? A full outer shell.
They can get this by getting electrons for giving them away.
Ex: Nitrogen has 5 valence electrons.
It can gain 3 to get a total of or,
It can lose 5 to drop to the lower level
Which do you think is more likely?

9. Examples:
Aluminum: How many valence electrons: How many does it need to get: How many can it give away: 3 5 3 Al

10. Examples:
Argon: How many valence electrons: How many does it need to get: How many can it give away: 8 8 Ar

11. + Cl Na = Cl Na How do they bond?
An atom that needs will get from an atom that gives.
Chlorine needs 1 electron and Sodium is happy to give one up. + Cl Na =
Cl Na

12. How about water?
Get a whiteboard and lets practice.

13. Homework
Worksheet on Lewis Structures.