1. Electrons

2. Number of Electrons: In a neutral atom:
Atomic # = # of protons = # of electrons

3. Valence Electrons:
Are the number of electrons in the outermost orbital.
The number of valence electrons stays the same as you go up/down a group, but they increase as you go from across the periodic table.
Valence electrons are quite possibly the most important electrons an atom has.
They get most involved in chemical reactions.

4. How to determine the # of valence electrons?

5. Example: Silicon

6. Electron/Lewis Dot Diagrams
An electron dot diagram consists of the element's symbol surrounded by dots that represent the valence electrons. 
Typically the dots are drawn as if there is a square surrounding the element symbol with up to two dots per side. 
An element will never have more than eight valence electrons.

7. Steps to drawing a Lewis Dot Structure:
Draw the symbol
Dots are added around the symbol to represent the # of valence electrons.
These only apply to representative elements.

8. Bohr Diagrams Picture representation of an atom.
Gives information about the nucleus and electron energy levels.

9. Steps to drawing a Bohr Diagram:
Write symbol, # of protons and # of neutrons.
Add circles to include all energy levels needed (same as period #).
Add electrons to each orbital until you have the correct # for a neutral atom.

10. Example: Aluminum