Help with oxidation numbers?

1. oxidation number atom in elemental form zero.
substance elemental if both of following true:
1 kind of atom present
charge = 0
examples:
s8: oxidation number of s = 0
fe: oxidation number of fe = 0

2. oxidation number of monoatomic ion = charge of monatomic ion.
examples:
oxidation number of s2- -2.
oxidation number of al3+ +3.

3.the oxidation number of group 1a metals = +1 (unless elemental).

4. oxidation number of group 2a metals = +2 (unless elemental).

5. hydrogen (h) has 2 possible oxidation numbers:
+1 when bonded nonmetal
-1 when bonded metal

6. oxygen (o) has 2 possilbe oxidation numbers:
-1 in peroxides (o22-)....pretty uncommon
-2 in other compounds...most common

7. oxidation number of fluorine (f) -1.

8. sum of oxidation numbers of atoms (or ions) in neutral compound = 0.

9.the sum of oxidation numbers of atoms in polyatomic ion = charge on polyatomic ion.

hf
cl4
na2o2
h2co3
no2
so4
hno3
n2o5

explanation please :)

Science & Mathematics Chemistry Next