1. Valence Electrons

2. Valence Electrons
the electrons that are in the highest (outermost) energy level
that level is also called the valence shell of the atom
they are held most loosely

3. The number of valence electrons in an atom determines:
The way that atom will bond with other atoms

4. As a rule, the fewer electrons in the valence shell, the more reactive the element is.
When an atom has eight electrons in the valence (outer) shell, it is stable.
All atoms are trying to fill their outer shell with 8 electrons

5. (ex) Lithium # of protons = 3 # of electrons = 3 # of neutrons = 4
Valence electron
The inner ring (or shell) holds 2 electrons.
The outer ring/shell holds 8 electrons.
If there are less than 8 for an atom, then it is unstable or incomplete.
The outer electrons are the valence electrons.
Lithium has a valence electron # of 1

6. Chemical Bonds
To fill their outer shells with 8 electrons, atoms make chemical bonds with other atoms.

7. They will bond to follow the octet rule.
Hydrogen (column 1) Chlorine (column 7)

8. Drawing Atoms
When scientists draw atoms to show how they chemically bond, they only draw the valence electrons.
We only use the valence electrons because those are the only ones involved in bonding.

9. Noble Gases Notice that there is a column #8.
This means those atoms have 8 valence electrons. Their outer shell is already complete!
These are called Noble Gases and they do NOT bond with other atoms.
Neon is in column 8. It already has 8 valence electrons.