How to Find Oxidation Numbers (Rules and Examples)

Using a list of simple rules you’ll learn how to find the oxidation numbers for elements and compounds. More oxidation help at Breslyn.org (and get all my free chem video guides)!

For each rule there are examples and practice calculating oxidation numbers.

Note: at 3:01 the oxidation number for N in N2O should be +1.

More practice calculating oxidation number: youtu.be/hTjSNTOUcBQ

Visit breslyn.org for more chemistry help and practice.


--- General Rules for Determining Oxidation Numbers ---

1. In a neutral compound all oxidation numbers must add up to zero.

2. In an ion the all oxidation numbers must add up to the charge on the ion.

3. Free elements have an oxidation number of zero (e.g. Na, Fe, H2, O2, S8).

4. Fluorine (F) = -1

5. Group 1 = +1 Group 2 = +2

6.Hydrogen with Non-Metals = +1 Hydrogen with Metals (or Boron) = -1

7. Oxygen = -2 (except with Fluorine or Peroxides)

8. Group 17(7A) = -1 Group 16 (6A) = -2 Group 15 (5A) = -3

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Full Explanations for compounds shown in video:

CaC2: -
ClO3- : youtu.be/AEETUgn5Tgw
FeCl3: youtu.be/7ZSP_kQCKOo
HCl: -
HF: youtu.be/dT3W_YRXawk
H2O2: youtu.be/MtX425dVoEQ
LiH: youtu.be/qm6U8RASiaU
NaCl: youtu.be/3YHC5Kbt_sA
N2O: youtu.be/gFWdQ2MNb48
Na2O2: -
NO: youtu.be/Ks67knKgjvA
OF2: youtu.be/MtX425dVoEQ
PF5: -
P4: youtu.be/71tm5PHGP2Q
NCl3: youtu.be/lKFp1cit1Q0