1. Electrons and Lewis Dot Structures
Seventh Grade Science

2. Electron Shells Atomic number = number of Electrons
Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.
Electron shells determine how an atom behaves when it encounters other atoms

3. Electrons are placed in shells according to rules:
The first shell can hold up to 2 electrons
The next shell holds up to 8 electrons
The third shell holds up to 18 electrons
The fourth shell holds up to 32 electrons

4. Octet Rule
Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons
C would like to Gain 4 electrons
N would like to Gain 3 electrons
O would like to Gain 2 electrons

5. Lewis Structures Find out which group (column) your element is in.
This will tell you the number of valence electrons your element has.
You will only draw the valence electrons.

6. Reviewing Groups Group 1 = 1 electron Group 8 = 8 electrons
Each column is called a group or family
Each element in a group has the same number of electrons in their outer orbital, also known as “shells”.
The electrons in the outer shell are called “valence electrons”
3, 4, 5, 6, 7

7. Drawing Lewis Dot Structures
Write the element’s symbol.
Determine which group the element is in so you can figure out the number of valence electrons.
Starting at the right, draw the number of electrons, or dots, counter-clockwise around the element symbol

8. Writing Lewis Dot Structures
Write the Lewis Dot structures for the following elements: H P Ca Ar Cl Al

10. Electron Dot Structures
Symbols of atoms with dots to represent the valence-shell electrons
H He:
          
Li Be  B   C   N   O  : F  :Ne :
       
          
Na Mg  Al  Si  P S :Cl  :Ar :
       

11. Learning Check A. X would be the electron dot formula for
A. X would be the electron dot formula for
1) Na 2) K 3) Al
 
B  X  would be the electron dot formula
1) B 2) N 3) P