TEACHER MASTER
Chemistry - Science 9
BOHR MODELS
In this set of notes we will cover:
- Draw a Bohr model of each atom up to atomic number 20
 Recommended time required for presentation of this set of notes:
o 45 minutes to 60 minutes depending on the group
 Materials Needed:
 Special Notes:
o By the end of the lesson students should find Bohr diagrams
relatively simple. Remind them to practice a few for homework as
they are easy to forget how to do.
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106750919
TEACHER MASTER
Chemistry - Science 9
BOHR MODELS
NAME _______________
DATE _______________
In this set of notes we will cover:
- Draw a Bohr model of each atom up to atomic number 20.
Reading the Periodic Table
For the first 20 elements of the periodic table you can “read”
how the electrons are arranged around the nucleus.
Rows represent levels (or layers) of the orbital.
Columns represent each electron added.
1st Row:
The first energy level can only hold two electrons. So there
are only two elements in the first row (hydrogen and helium).
He
2 p+ 2 n0
H
1 p+
2nd Row:
The second energy level can hold eight electrons (2 columns
+ 6 more columns). So there are eight elements in the
second row. Here are the first three:
Li
3 p+ 4n0
Be
4 p+ 5n0
B
5 p+ 6n0
106750919
TEACHER MASTER
Chemistry - Science 9
Bohr Models
Instead of continuing to draw all these circles a Bohr diagram
simplifies things for us. A Bohr diagram just shows the
nucleus and indicates how many electrons are in each level.
After figuring out how many electrons an atom has count out how many are in each layer.
Remember: the first layer can hold two electrons. The second and third can hold eight.
If you forget … just count the number of elements in each row.
Lithium
3 p+
4 n0
Oxygen
-
2e
-
1e
Berylium
4 p+
5 n0
2e-
2e-
6e-
9 p+
10 n0
2e-
7e-
2e-
8e-
2e-
8e-
Neon
2e-
3e-
Carbon
6 p+
6 n0
2e-
Flourine
Boron
5 p+
6 n0
8 p+
8 n0
10 p+
10 n0
Sodium
-
2e
4e-
2e-
5e-
11 p+
12 n0
1e-
Nitrogen
7 p+
7 n0
106750919
TEACHER MASTER
Chemistry - Science 9
You try a few
Complete the following Bohr Diagrams:
Magnesium
12 p+
12 n0
2e-
8e-
2e-
2e-
8e-
8e-
2e-
8e-
7e-
2e-
7e-
Calcium
20 p+
20 n0
2e-
Chlorine
17 p+
18 n0
Fluorine
9 p+
19 n0
Hydrogen
1 p+
0 n0
1e-
You will need to be able to draw or identify the Bohr diagrams
for the first 20 elements.
Quiz Next day: Bohr Model – first 20 elements
106750919