1. Valence Electrons!

2. One of the most important, if not the most important concept in chemistry!

3. What are they? The number of electrons in the outer shell of an atom. The number of electrons in the outer shell of an atom. The number of valence electrons determines what elements react with. The number of valence electrons determines what elements react with. An atom usually can have up to 8 valence electrons (octet rule). An atom usually can have up to 8 valence electrons (octet rule). All atoms want 8 valence electrons, this means they are stable. All atoms want 8 valence electrons, this means they are stable.

4. Valence Electrons: based on Group number. 1A 2A 3A4A5A6A7A 8A 1 2 34567 8 1 1 1 1 1 1 2 2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5 6 6 6 6 7 7 7 7 8 8 8 8 8 Multiple Valences

5. 1) Zn 2) K 3) I 4) Au 5) Al 6) Se 7) F Total vs. Valence Electrons Determine the TOTAL number of e- and then the valence e-. Transition metal? List it as “multiple”. 8) Ra 9) C 10) O 11) Ar 12) U 13) Ca 14) V

6. Dot Diagrams Simple diagram using the element’s symbol surrounded by dots representing the number of valence electrons

7. 1. Determine the # of valence electrons 2. Write down the element’s symbol 3. Starting on the right hand side, moving clockwise, add the dots (N,S,E,W) 4. Dots will not pair up until they are forced (likes repel) Example: Hydrogen H Valence e - = 1

8. More Examples 1. Carbon 2. Nitrogen 3. Oxygen 4. Bromine C Valence e - = 4 Valence e - = 5 N Valence e - = 6 O Valence e - = 7 Br

9. What group has 8 valence e - ? 8A: The noble/inert gases! Every element is jealous of the noble gases. 8A is where the party is. Everyone wants to go to the party!

10. Octet Rule Elements either gain or lose electrons Elements either gain or lose electrons They are lazy so they either gain up to four or lose up to four to get to 8 OR to lose all in the outer shell They are lazy so they either gain up to four or lose up to four to get to 8 OR to lose all in the outer shell

11. Gain or Lose? 1. Boron 2. Nitrogen 3. Cesium 4. Bromine B N Cs Valence e - = 3 Br Lose Lose Gain Gain Valence e - = 1