1. The Bohr Model Valence Electrons

2. Chemical Behaviors
Scientists observe that elements within the same group have similar behaviors.
It was proposed that the number and position of electrons found in an atom must have an effect on chemical behaviors.

3. The Bohr Model
The Bohr Model represents atoms with their electrons in successive energy levels surrounding the nucleus.
Each energy level has a limited capacity to hold electrons. (2-8-8)

4. Sample Bohr Model Consider aluminum (Al):
The nucleus is drawn in the center.
13 protons
14 neutrons
13 p+
13 electrons
14 n0
The first energy level holds only 2 electrons.
3 valence electrons
The second and third energy levels hold only 8 electrons.

5. Bohr Model Comparison
Draw and compare Bohr Models of lithium (Li) and sodium (Na).
How many valence electrons are present in each atom?
Elements in the same group have the same number of electrons available for bonding.

6. Bohr Model Practice A B C D
1) Which Bohr Model below represents an atom of oxygen? A B B C D

7. Bohr Model Practice A B C D
2) Which Bohr Model below represents an atom of sulfur? A B C C D

8. Bohr Model Practice
3) Draw Bohr Models of the following atoms (write-in protons & neutrons):
silicon-29
nitrogen-14
magnesium-24
phosphorus-31

9. Bohr Model Practice
4) Which of these four atoms would most likely have similar chemical behaviors?
silicon-29
nitrogen-14
magnesium-24
phosphorus-31
N and P