1. Created by G.Baker www.thesciencequeen.net
Atom Models
There are two models of the atoms we will be using in class.
Bohr Model
Lewis Dot Structure
Created by G.Baker

2. Created by G.Baker www.thesciencequeen.net
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. - + + -
Created by G.Baker

3. Purpose of the Bohr Model
Bohr models are used to predict reactivity in elements.
Reactivity refers to how likely an element is to form a compound with another element.
2. When looking at Bohr models, we look at its valence electrons (the electrons on the last energy level) to determine reactivity.

4. Electrons have special rules….
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.
Only so many can be in any certain shell.
Created by G.Baker

5. You must fill one level before going on to draw the next level!
Nucleus
1st shell or orbit
2nd shell or orbit
3rd shell or orbit
Level 4 can hold a max of 32e
Adapted from
Created by G.Baker

6. Electrons have special rules….
The electrons in the outer most shell of any element are called valance electrons.
Created by G.Baker

7. Created by G.Baker www.thesciencequeen.net
So let’s try it….
How to draw a Lithium atom
First, look at the Periodic Table
Second, determine the number of protons the atomic number)
Then determine the number of neutrons (Atomic mass – atomic number)
Then determine the number of electrons the atomic number) 3 Li
Lithium 7
Created by G.Baker

8. Created by G.Baker www.thesciencequeen.net
So let’s try it….
Protons = 3 3 Li
Lithium 7 - + + + - -
Electrons = 3
2 in the 1st shell, 1 in the 2nd shell
Neutrons = 4
(7-3=4)
Created by G.Baker

9. 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

10. 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

11. 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

12. Created by G.Baker www.thesciencequeen.net
Lewis Dot Structure
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. + - • O • • •
• •
Created by G.Baker