1. Bohr Model & Lewis Dot Diagrams
Modern Atomic Theory

2. Recall...

3. Atom Models
Bohr Model
Lewis Dot Structure

4. Bohr Model The Bohr Model shows all of the particles in the atom.
In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N.
In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e.

5. Bohr Model continued…..
Bohr models are used to predict reactivity in elements.
Reactivity - how likely an element is to form a compound with another element.
When looking at Bohr models, we look at its valence electrons (the electrons on the last energy level) to determine reactivity.
You can’t just shove all of the electrons into the first orbit of an electron.
Electrons live in something called shells or energy levels.

6. Drawing Bohr Models Draw the nucleus FIRST
Write the number of neutrons and the number of protons in the nucleus SECOND
Draw the first energy level THIRD
Draw the electrons in the energy levels according to the rules below. Make sure you draw the electrons in pairs.
Keep track of how many electrons are put in each level and the number of electrons left to use.

7. Rules for Energy Levels
Level 1 (closest to the nucleus) can hold a maximum of 2e.
Level 2 can hold a max of 8e.
Level 3 can hold a max of 18e.
Level 4 can hold a max of 32e.
You must fill one level before going on to draw the next level!

8. Maximum # of Electrons for that Energy Level Valence
Row #
# of Elements in the Row
Maximum # of Electrons for that Energy Level
Valence 1 2
# of electrons in outermost shell 8 3 4 32

10. Guided Practice
In order to draw Bohr models of these elements, you must first determine the number of protons, neutrons, and electrons. Once you have found this information, follow the directions to draw your model. 6 6 6 6 C
Carbon
12.011
Protons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model: 2 4

11. Guided Practice 16 S
Sulfur
32.066 16 16 16
Protons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model: 3 6

12. Guided Practice Protons: _____ Neutrons: _____ Electrons: ______3 Li
Lithium
6.941
Protons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model: 3 4 3 2 1

13. Guided Practice 10 10 10 10 Ne
Neon
20.180
Protons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model: 2 8

14. Guided Practice 15 16 15 15 P
Phosphorus
30.974
Protons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model: 3 5

15. Guided Practice 11 12 11 11 Na
Sodium
22.990
Protons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model: 3 1

17. Lewis Dot Diagrams
The Lewis Dot Structure is a bit different from the Bohr model.
It only shows the element symbol and it’s outer most electron shell.

18. How to write a Lewis Dot Structure
Step 1: Write the Element Symbol
Step 2: Find the number of electrons in the last energy level of the Bohr Model (Valence Electrons)
Step 3: Place the electrons (dots) around the symbol in clockwise order so that there are no more than 2 electrons per side.

19. Elements in the same row = PERIOD
Elements in the same column = GROUP