The lazy person's guide to oxidation
numbers of atoms in compounds and ions.:
-
This list is a hierarchy, if there is a conflict between rules, the
first listed rules.
-
The oxidation numbers for a compound add up to zero and for an ion to
the charge.*
-
fluorine has an oxidation number of -1
-
Group 1 metals have an oxidation number of +1
-
Group 2 metals have an oxidation number of +2
-
Sc, Y and Al have an oxidation number of +3
-
H is +1 when bonded with a nonmetal and -1 when bonded with a metal
-
Oxygen has an oxidation number of -2 (learn the polyatomic ions)
-
Group 17 nonmetals have an oxidation number of -1
-
Group 16 nonmetals have an oxidation number of -2
-
Group 15 nonmetals have an oxidation number of -3
-
Carbon has an oxidation number of -4
The polyatomic ion chart:
Name(acid) ion:
acid: |
hypo...ite
hypo...ous |
...ite
...ous |
|
...ate
...ic |
per...ate
per...ic |
chlor |
ClO- |
ClO2- |
|
ClO3- |
ClO4- |
brom |
BrO- |
BrO2- |
|
BrO3- |
BrO4- |
iod |
IO- |
IO2- |
|
IO3- |
IO4- |
sulf(ur) |
SO22- |
SO32- |
|
SO42- |
|
nitr |
|
NO2- |
|
NO3- |
|
|
|
|
|
|
|
phosph(or) |
PO23- |
PO33- |
|
PO43- |
|
carbon |
|
|
|
CO32- |
|
chrom |
|
|
|
CrO42- |
|
dichrom |
|
|
|
Cr2O72- |
|
mangan |
|
|
|
|
MnO4- |
Others:
hydroxide: OH- |
hydronium: H3O+ |
ammonium: NH4+ |
Some special polyatomic ions for which O does not have an oxidation
number of -2
peroxide O22- |
superoxide O2- |
*Some implications of this rule are:
-
The oxidation number for an element in its elemental state is 0.
-
The oxidation number for a monatomic ion of one atom is the same as its
charge
-
The oxidation number for a monoatomic ion with more than one atom is its
charge divided by the number of atoms per ion.