1. Bohr Models and Lewis Dot Structures

2. Recall that electrons are NOT in the nucleus of the atom! A VERY simple way to think about the positions of atoms are in terms of energy levels. Energy Levels –Closest to nucleus Lower energy level –Farthest from nucleus Higher energy level Each energy level can hold only a certain number of electrons.

3. Energy Levels hold certain numbers of Electrons. All of the energy levels together are called the electron cloud. First Energy Level –Can hold 2 electrons Second Energy Level –Can hold 8 electrons Third Energy Level –Can hold 8 electrons Fourth Energy Level –Can hold 8 electrons

4. THE TRUTH!!!

5. Let’s Draw a Picture of an Argon Atom. You know how many protons, electrons, & neutrons are in an atom of any element. Now, draw it. How many e- are in the … First Energy Level? Second? Third? Fourth? This is called a Bohr Model!! 18P 14N

6. Notice how the Electrons come in pairs? ALWAYS FILL THEM IN as such: –Up, down, side, side. Up, down, side, side.

7. Bohr Models We call this model the Bohr Model, after Neils Bohr who developed it in 1915.

8. BOHR MODEL It has a circle in the center, which represents the nucleus. We write the number of protons and neutrons in this circle. The rings surrounding the circle are the energy levels. We draw electrons on the energy levels.

9. Let’s Try a Bohr Model of a Lithium Atom.

10. Did you get it right?

11. One More Practice Problem… Draw a Bohr model of Oxygen.

12. Did you get it right?

13. Term to Know Valence Electron – number of electrons in the outer energy level. What is the Valence Electron number for Lithium? 1 Oxygen? 6

14. Here’s a short-cut! Lewis Dot Structures Only use the element’s symbol and the valence electrons. Write the symbol and surround it with the correct number of valence electrons.

15. Lithium Lewis Dot Bohr Model

16. Oxygen Bohr Model Lewis Dot