1. Catalyst: 10.27.2008 Find the atomic #, mass #, # protons, # electrons, and # neutrons for the following elements: Beryllium & Lithium

2. Objective  Explain how electrons are placed in the electron cloud.  Identify valence electrons  Make atomic diagrams with proper electrons  Construct Lewis Dot Diagrams to show valence electrons

3. Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008

4. Electron Location  Where are electrons located in an atom?  Outer electron cloud  What do they do there?  Constantly moving  How are they arranged in the electron cloud?  In a specific pattern called energy shells (or levels)

5. Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008 Electron Location -e - constantly moving & found in electron cloud - arranged in energy shells/levels

6. Energy Shells  Each shell or level has a specific amount of energy (E)  Each shell can only hold a certain amount of electrons.

7. Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008 Electron Location Energy Shells/Lev els -e - constantly moving & found in electron cloud - arranged in energy shells/levels - each level has specific amt. of energy

8. Energy Shells  Each energy shell/level is represented by a circle around the nucleus of the atom.  The first (lowest) energy level holds only 2 electrons  After this level is filled up, electrons go to a higher (outer) E level.  Electrons fill the lower levels and then move to higher (outer) levels.

9. Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008 Electron Location Energy Shells/Lev els -e - constantly moving & found in electron cloud - arranged in energy shells/levels - each level has specific amt. of energy - 1 st energy level: 2 e - maximum - after a level is filled up, e - go to higher (outer) energy levels

10. Energy Shells  No matter how many energy levels there are, the outermost energy level can only hold at most 8 electrons  The outermost energy level is called the valence shell.

11. Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008 Electron Location Energy Shells/Lev els -e - constantly moving & found in electron cloud - arranged in energy shells/levels - each level has specific amt. of energy - 1 st energy level: 2 e - maximum - after a level is filled up, e - go to higher (outer) energy levels - valence shell – outermost energy level / can hold @ most 8 e -

12. Energy Shell Example (Left page)  Carbon:  What is its symbol?  What is the atomic number?  What is the atomic mass?  How many protons does it have?  How many electrons does it have?  How many neutrons does it have?  How many electrons go in the first shell?  How many electrons go in the next shell?  How many valence electrons are there?

13. Energy Shell Example (Left page)  Carbon:  What is its symbol? C  What is the atomic number? 6  What is the atomic mass? 12  How many protons does it have?  How many electrons does it have?  How many neutrons does it have?  How many electrons go in the first shell?  How many electrons go in the next shell?  How many valence electrons are there?

14. Energy Shell Example (Left page)  Carbon:  What is its symbol? C  What is the atomic number? 6  What is the atomic mass? 12  How many protons does it have? 6  How many electrons does it have? 6  How many neutrons does it have?  How many electrons go in the first shell?  How many electrons go in the next shell?  How many valence electrons are there?

15. Energy Shell Example (Left page)  Carbon:  What is its symbol? C  What is the atomic number? 6  What is the atomic mass? 12  How many protons does it have? 6  How many electrons does it have? 6  How many neutrons does it have? 6  How many electrons go in the first shell? 2  How many electrons go in the next shell? 4  How many valence electrons are there? 4

16. Energy Shell Example (Left page)  Carbon:  What is its symbol? C  What is the atomic number? 6  What is the atomic mass? 12  How many protons does it have? 6  How many electrons does it have? 6  How many neutrons does it have? 6  How many electrons go in the first shell? 2  How many electrons go in the next shell? 4  How many valence electrons are there? 4

17. Energy Shell Example #2 (Left page)  Draw an atomic diagram for Helium.  How many valence electrons are there in Helium?

18. Energy Shell Example #2 (Left page)  Draw an atomic diagram for Helium.  How many valence electrons are there in Helium? 2e - 2 p + 2 n 0 e-e- e-e-

19. Lewis Dot Diagrams  Lewis Dot Diagrams are a way to show you how many valence electrons are in an atom.  How many valence electrons were in Carbon?  4 valence e -  Lewis Dot Diagram of Carbon:

20. Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008 Lewis Dot Diagram -Show how many valence electrons in an atom. -

21. Lewis Dot Diagram Practice (Left Side)  Draw the Lewis Dot Diagram for each of the following: 1. Element X has 2 valence electrons. 2. Element Y has 5 valence electrons. 3. Element Z has 7 valence electrons.

22. Practice Problems  You will create an atomic diagram with correct number of energy levels AND a Lewis Dot diagram for each of the of following elements: Boron, Nitrogen, Phosphorous, Chlorine, and Fluorine. 2 p + 2 n 0 e-e- e-e-