1. Notes – Determining Oxidation Number Who Gains? Who Loses?

2. Background Information/Terms Ion- an atom with a positive or negative electric charge. Valence energy level- the outermost (highest) energy level. Valence electrons- the electrons found in the outermost energy level.

3. Background Information/Terms Family numbers- the numbers at the top of the periodic table that (with some modification) tell how many valence electrons an atom has. Octet rule- a rule (that is generally true) which states that an atom with a full valence energy level is stable. Oxidation number - the number of electrons that an atom gains, loses or shares in order to form chemical bonds.

4. Facts about Elements and Their Oxidation Number - Metals Metals lose their valence electrons when they become ions. This gives metals a full outermost energy level. Metal ions have a positive (+) charge. The number of electrons a metal loses becomes its oxidation number.

5. Facts about Elements and Their Oxidation Number - Nonmetals Nonmetals gain electrons until they get 8 electrons in their outermost energy level. Nonmetal ions have a negative (-) charge. The number of electrons a nonmetal gains becomes its oxidation number.

6. Oxidation number Oxidation number - the number of electrons that an atom gains, loses or shares in order to form chemical bonds. The oxidation number determines two things: –How the element will bond –What elements will bond with it

7. Review Elements want to have a stable atomic structure. Stable atoms have full outer energy levels If an element has only one energy level, it is full with 2 electrons Although the third levels hold more than 8, atoms think their energy levels are full with 8 electrons Some elements gain electrons to get full while other will lose electrons to empty out a level.

8. Summary It is easier to gain one or two electrons than to lose 6 or 7 and vice versa. Family ## of valence electrons gain or loseOxidation number 11Lose 1+ 1 22Lose 2+ 2 133Lose 3+ 3 144Gain or lose 4+/- 4 155Gain 3- 3 166Gain 2-2 177Gain 1 188Already full0