1. Bohr Model & Lewis Dot Diagrams

2. Recall...

3. There are two models of the atoms we will be using in class.
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. 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.
The electrons in the outer most shell of any element are called valance electrons.

6. 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

8. Energy level 3 CAN hold 18, but the elements in the first few periods only use 8!

9. Try an Example! 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)

11. Try the following elements on your own:Al Ne K

12. 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.

13. 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.