1. Valence Electron Interaction and Charges

2. The Role of Electrons in Bonding The sharing or transfer of electrons is what holds atoms together in a compound Typically, only the electrons in the outer energy level are used for bonding. These electrons are called Valence Electrons The outer energy level is called the Valence Shell

3. Comprehension Check How many electron shells does phosphorus have? 3 How many valence electrons does phosphorus have? 5

4. PWYR – Valence Schmalence tin 4 arsenic 5 strontium 2 bromine 7 sodium 1 tellurium 6 gallium 3 krypton 8

5. Bonding Ionic Bonds – Results from the complete transfer of electrons Results in a formation of two charged atoms called ions The atom that gains electrons becomes negatively charged and is called an anion The atom that loses electrons becomes positively charged and is called a cation

6. Octet Rule Octet Rule: atoms want to have a full valence shell (8 valence electrons) Atoms react with one another in an attempt to gain or lose electrons to fill their valence shell During a reaction, electrons can be shared or completely transferred Two options Gain electrons to fill valence shell Lose electrons to reveal full shell below outer shell (outer shell)

7. Oxidation Numbers Oxidation Numbers tell us how many electrons an atom is willing to lose or gain Positive oxidation numbers indicate that the atom can lose that many electrons Negative oxidation numbers indicate that the atom can gain that many electrons Some atoms have more than one possibility Transition Metals

8. Alkali and a Halogen Valence Electrons Extra Electron Missing Electron

9. valence electron = 1 Easier to give away for full valence shell Cation = positive -getting ride of negative particle Charge = +1 valence electron = 7 Easier to take in for full valence shell Anion = Negative - taking in negative particle Charge = -1

10. Periodic Table Groups have same valence electrons Same oxidation number 1 +1 2 +2+3 34 +/- 4 5 -3 6 -2 7 0 8

11. Comprehension Check- To Gain or Not to Gain Nitrogen  Beryllium  Xenon  carbon  Oxygen  Lithium  Chlorine  Boron  Gain 3 Lose 2 None Gain/Lose 4 Gain 2 Lose 1 Gain 1 Lose 3