Rule 1

1
Rule 1 The oxidation number for an atom of any
free (uncombined) element is ZERO. Examples Na,
Ca, Br2 have zero oxidation number.
2
Rule 2 The oxidation number for a simple ion is
the charge on the ion Cl- -1, Na 1
3
Rule 3 In non metal hydrogen containing
compounds, oxidation number of hydrogen is 1
(HCl).
4
Rule 4 In metal hydrogen containing compounds,
oxidation number of hydrogen is - 1 (when H
combines with alkali metals or alkaline earth to
form hydrides of metals such as NaH, LiH,
CaH2.).
5
Rule 5 In compounds involving the group 1 alkali
metals, the elements are assigned oxidation
number of 1. Na 1
6
Rule 6 In compounds involving the group 2
alkaline earth metals, the elements are assigned
oxidation number of 2. Ca2 2
7
Rule 7 Oxygen is usually assigned an oxidation
number of -2 for oxides. It has an oxidation
number of -1 in peroxides (H2O2).
8
Rule 8 Fluorine always has oxidation number of -1
in compounds. The other elements in group VII the
HALOGENS is usually -1 in compounds with elements
of low electronegativity.
9
Rule 9 The sum of oxidation numbers of all the
atoms in the formula for a neutral compound is
ZERO.
10
Rule 10 The sum of oxidation numbers of a
polyatomic (compound ion ) or complex ion is the
same as the charge on that ion