1. Valence Electrons & Bohr Diagrams

2. Atomic Structure
Atoms have a nucleus that contains Protons and Neutrons
Electrons are contained in shells that surround the nucleus
An atom is made of mostly empty space
Protons have a positive charge
Electrons have a negative charge
Neutrons are Neutral

3. Valence Electrons Electron Shell Number of Electrons 1 2 8 3 4 18 5 6
Each electron shell can hold a certain number of electrons
Electron shells are filled from the inside out
Noble Gases have full outer electron shells
All other elements have partially filled outer electron shells
Electron Shell
Number of Electrons 1 2 8 3 4 18 5 6 32 7

4. Valence Electrons
The electrons in the outer most electron shell are called valence electrons
The shell containing electrons that is furthest from the nucleus is called the valence shell
The number of electron shells with electrons is the same as the period number

5. Noble Gas Stability Noble gases are usually unreactive
This is because they have full valence shells
An element with a full valence shell is a happy element 
For two atoms to join together atoms must gain, lose or share electrons
Elements with full valence shells do not easily gain or lose electrons

6. Noble Gas Stability Atoms want to gain stability
Atoms will try to gain or lose electrons to have a full valence shell
Metals try to lose electrons
Non-Metals try to gain electrons

7. Becoming An Ion Electrons are negatively charged
Protons are positively charged
Neutral atoms do not have a charge because the number of protons is the same as the number of electrons
When atoms gain or lose electrons they become positively or negatively charged
An atom with a charge is called an Ion

8. The Octet Rule
To draw the electron configuration of a neutral atom, look at the ATOMIC NUMBER.
Neutral atoms have the same number of electrons and protons
The first shell only holds 2 electrons
Every other shell is filled up to 8 electrons
The “left over” electrons are found on the last shell. The last shell is the valence shell and these electrons are called valence electrons.
Valence electrons tell us which atoms will likely combine with others in order to ‘share’ 8 electrons on their last shell. All matter wants to be stable.

9. ATOMIC MASS
The atomic mass tells us how heavy an atom is. The mass is calculated by the total protons and neutrons in the nucleus of an atom.
Electrons are so tiny their mass is not counted in the overall mass of an atom. Their mass is considered negligible.