Feb 02, 2016
An oxidation number is the charge that an atom in a compound would have if the electron pairs in the bond belonged solely to the more electronegative atom.
1. The oxidation # of an atom in its pure form, such as Na or Fe, or in a
molecule of that element only, such as O2 or P4,
is ZERO.
2. The oxidation # of a monatomic ion is the charge on the ion.
ex. Ca2+ is +2
3. a) O = -2 except in H2O2 (-1)
b) H = +1 except in metal hydride, ex. LiH (-1)
c) Group IA = +1d) Group IIA = +2e) Halides = -1
4. Use charges on polyatomic ion as indicator, examples: SO4
2- , NO3-
The algebraic sum of the positive & negative oxidation #’s of the atoms in a polyatomic ion is equal to the charge on the ion.
example: SO42-
5. The sum of the positive & negative oxidation #’s in a neutral compound is zero.
example: K2Cr2O7
1. What is the single oxidation number of manganese (Mn) in:
a) MnO2
b) Mn2O7
c) MnO42-
d) KMnO4
2. Determine the single oxidation # of the underlined atom in each of the following species:
a) CrO42-
b) P4O10
c) Fe3O4
d) S2O32-