1. Modeling and Representing Atoms on Paper
How to draw Bohr Diagrams and Electron Dot Diagrams (sometimes called Lewis Structures)

2. Bohr Diagrams Pictographic representation of an Atom
Shows information about the nucleus
Electron energy levels
Good for index cards and flash cards

3. Bohr Diagrams
Start with a rectangle about 2” x 4”

4. Bohr Diagrams
At the top write the name, Atomic number, Mass number of the element and the atomic mass
Carbon
Atomic # = 6
Mass # = 12
Atomic mass = amu

5. Bohr Diagrams
Draw a small circle below the text that will represent the nucleus of the atom
In the circle write:
the elemental symbol
the number of Protons
the number of Neutrons
Carbon
Atomic # = 6
Mass # = 12
Atomic mass = amu
C 6p+
6n0

6. Bohr Diagrams
Draw a larger circle around the nucleus circle to represent the first energy level for electrons
Add more circles outside to include all of the energy levels you need for the atom.
(Hint: In what period is the element?)
Carbon
Atomic # = 6
Mass # = 12
Atomic mass = amu
Carbon is in Period two and therefore needs two energy levels
C 6p+
6n0

7. Bohr Diagrams
Now add electrons, as small dots, to each energy level as allowed until you have the proper number of electrons for a neutral element.
Remember:
Carbon
Atomic # = 6
Mass # = 12
Atomic mass = amu
Energy Level
# of e- 1 2 8 3
The number of electrons should be equal to the number of protons.
C 6p+
6n0
If you need a third level make your circles a little smaller.

8. Bohr Diagrams You now have a complete Bohr Diagram Carbon Atomic # = 6
Mass # = 12
Atomic mass = amu
C 6p+
6n0

9. Electron Dot Diagrams Also called Lewis Structures
Representation of valence electrons only
Useful only for “Representative elements”
Gives some indication of the geometry (shape) of compounds when used for bonding diagrams
Easy to draw

10. Electron Dot Diagrams C
The Elemental Symbol serves as the representation of the nucleus C

11. Electron Dot Diagrams C
Dots are added around the nucleus to show electrons only in the outer energy level
Like the Hund rule add 1 electron per side, then add more as needed. C
Carbon has only 4 electrons in the 2nd energy level so we need only represent those 4

12. Electron Dot Diagrams C
Lewis structures only apply to “Representative elements” (Group A elements)
The maximum number of electrons that can be shown are 8 C
Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

13. Electron Dot Diagrams O
Lewis structures only apply to “Representative elements” (Group A elements)
The maximum number of electrons that can be shown are 8 O
Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

14. Electron Dot Diagrams Cl
Lewis structures only apply to “Representative elements” (Group A elements)
The maximum number of electrons that can be shown are 8 Cl
Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

15. Electron Dot Diagrams Li
Lewis structures only apply to “Representative elements” (Group A elements)
The maximum number of electrons that can be shown are 8 Li
Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

16. Electron Dot Diagrams Fe Cu Ag Pb
Transition metals don’t have valence electrons. They have Oxidation Numbers +2 +2 +2 +4
Fe Cu Ag Pb
We’ll Talk about Oxidation Numbers Next Week!