1. Oxidation States

2. Oxidation State: the apparent charge that an atom would have if electron pairs in covalent bonds belonged entirely to the more electronegative atom
Oxidation Number: positive or negative number assigned to an atom based on its oxidation state
“Electron bookeeping”

3. Common Oxidation Numbers (p. 658)
Atom or Ion
Oxidation #
Examples
atoms in elements
Fe, C, O2, F2
hydrogen +1
HCl, NH3
hydrogen with metals -1
NaH, CuH2
oxygen -2
H2O, FeO, NO3-
oxygen in peroxides
H2O2
monoatomic ions
ion charge
Mg2+, Na+, S2-

4. Determining Oxidation Numbers
Assign common oxidation numbers
The sum of oxidation numbers for a compound is 0
The sum of oxidation numbers for a polyatomic ion is its charge
Use algebra to determine any unknown oxidation numbers
Examples:
K2SO4 K2Cr2O7 MnO4-

5. CH4(g) + 2O2(g)  CO2(g) + 2H2O(l)
Redox Reactions
Oxidation numbers change in a redox reaction
Oxidation is an increase in oxidation number
Reduction is a decrease in oxidation number
Ca(s) + Cl2(g)  CaCl2(s)
CH4(g) + 2O2(g)  CO2(g) + 2H2O(l)

6. Practice Oxidation States of Vanadium Activity
p. 659 #12-14, 15a, 16, 17
p. 662 #18-20
p. 663 #1, 2, 5-8, 10