1. Compounds
Video Clip: Why it Matters

2. NOTES 2: VALENCE ELECTRONS, LEWIS DOT DIAGRAMS, AND OXIDATION NUMBERS

3. Review: Bohr’s Electron Model
1. How many total electrons are in a neutral atom of Sulfur? 2. How many electrons are in sulfur’s highest energy level (it’s most outer shell)(HINT: use the picture to the right)?
3. How many electrons does sulfur need to gain or lose in order to have 8 valence electrons (electrons in the outermost shell)?

4. Recap: Bohr’s Electron Model
Bohr developed an atomic model in which the electrons are arranged in specific energy levels.
The lowest level (n=1) is located closest to the nucleus. The highest level is located farther away from the nucleus.

5. Recap: Bohr’s Electron Model
*The electrons in the highest energy level for any element are known as valence electrons.*
Valence electrons are involved in chemical bonding.
Bonding and Valence Electrons Video Clip

6. Valence Electrons: Valence Electrons can be easily found by looking at the Group number or “A” number located above the column where the element is located on the periodic table.

7. Examples: Al= Group # ___ and ____A so it has ___ valence electrons
Examples: Al= Group # ___ and ____A so it has ___ valence electrons. Pb= Group # ___ and ____ A so it has ____ valence electrons. 13 3 3 14 4 4

8. Valence Electrons the Quick and Easy Way
Determine the number of valence electrons.
Phosphorus
Argon
Lead
Barium
5 valence electrons
8 valence electrons
4 valence electrons
2 valence electrons

9. Exceptions * This ONLY works for Group A Elements
(the Representative Elements)
Helium  two valence electrons

10. Label the Valence Electrons for each Column on the Periodic Table

11. LEWIS DOT DIAGRAMS: is a diagram in which the chemical symbol of an element represents the nucleus and the inner energy level and “dots” represent the valence electrons. There can only be up to 8 valence electrons and thus only 8 dots around a symbol. The first 4 dots are single and then they pair up as more are added. Octet rule states that all atoms wish to be like the Nobel gases (group 18) with a full valence of 8 electrons.

13. One Dot for Each Valence Electron
Lewis Dot Diagrams
Element Symbol
One Dot for Each Valence Electron

14. How Are the Dots Arranged?1 5 X 8 2 4 6 7 3

15. F He Ne C Example Dot Diagrams
Draw the dot diagrams for each of the following elements.
Helium
Carbon
Fluorine
Neon F He C Ne

17. Oxidation numbers OXIDATION NUMBERS: is the number of electrons an
atom gains, loses, or shares when it
forms a chemical bond and achieves the octet rule.
This will also be the charge of the ION.
Metals as a rule lose electrons and will have a (+) charge.
Nonmetals will gain electrons and have a ( -) charge
Nobel gases in group 18 will not
lose or gain and have a 0 charge

18. Label the periodic table for the ion charge created as atoms achieve the Octet rule (full valence of 8):

19. 4 4
+-4 -1 7 8

20. Complete homework page 6