1. Valence Electrons & Bohr Diagrams

2. Learning Goal Today’s learning goal is for students to:
For students to recall knowledge of the atomic structure & valence electrons
For students to develop their knowledge of Bohr Rutherford Diagrams
For students to apply their knowledge of valence electrons to drawing Lewis Dot Diagrams

3. RECALL: 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

4. Valence Electrons Electron Shell Number of Electrons 1 2 8 3 4 18 5 632 7
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

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. Bohr-Rutherford Diagrams

8. Two Important Scientists
The Bohr atom model and the Rutherford atom model of the atom were put together to come up with the Bohr-Rutherford model of the atom
The Bohr-Rutherford model allows the subatomic particles to be visible to the eye

9. Four Steps To Draw A Bohr-Rutherford Diagram
Draw the nucleus
Write
P – Number of Protons &
N - Number of Neutrons
in the middle of the nucleus
Nucleus

10. 3. Follow the octet rule
The octet rule is a chemical rule of thumb that says how electrons should be arranged in each orbital when drawing Bohr- Rutherford Diagrams
Where:
The 1st orbit has a max of 2 electrons
The 2nd orbit has a max of 8 electrons
The 3rd orbit has a max of 8 electrons

11. 4. Fill in # Electrons in orbitals
Na - Sodium
Remember the Octet Rule
2, 8, & 8
When filling in electrons, pair them up electrons leaving lone electrons to the end
Example: Sodium (Na)
Has Atomic # 11
Has Atomic Mass of 23
P –
E –
N - ●
11 P
12 N ●

12. 4. Fill in # Electrons in orbitals●
Draw electron orbitals as needed
Use dots to represent the number of electrons each element has
The electrons on the most outside orbital are the Valence Electrons ● ● ● ● ●
11 P
12 N ● ● ● ● ●

13. Example

14. Worksheet Time!
Bohr Rutherford Diagrams!

15. Lewis Dot Structures
Sometimes it can take a while to draw every single electron in a diagram – as in Bohr Rutherford Diagrams
So Gilbert Newton Lewis, an American physical, came up with an idea to simplify drawing atomic structures
We now use his Lewis dot structures to show how many valence electrons an element has
These dots can also represent bonds when put with another element