1. Redox Reactions of Nonmetals
Read pp

2. Redox and Non-Metals Redox rxns can involve non-metals!
Eg. burning of fossil fuels result in sulfur (S) and oxygen gas (O2), which are both non-metals, forming SO2 (sulfur dioxide)
However, redox rxns involves knowing the oxidation numbers (+, -, 0). Harder to do with non-metals!

3. Sulfur and oxygen are both commonly known to have a charge of -2
How do we do this with SO2?
This is where we use the rules of oxidation numbers…

4. Oxidation Numbers (ONs)
Ion charges and ONs are not the same thing!
Oxidation number = + or - number corresponding to the theoretical charge that an atom in a molecule or ion would have if the electron pairs in covalent bonds belonged entirely to the more electronegative atom

5. ONs are based on set rules
The sum of all ONs of the atoms in a compound must equal ZERO
The sum of all ONs of the atoms in a polyatomic ion must equal its charge

6. Going back to the SO2 example:
Which is more electronegative?
Oxygen is more EN than sulfur (3.2 vs 2.5), so the charge for oxygen will be -2

7. SO2

8. Rules for Oxidation Numbers
Elements
Elements on their own are always 0
Group I and II
Group I is +1; Group II is +2
Simple and Polyatomic Ions
The charge on the simple ion is the oxidation number
The sum of ONs in a polyatomic ion must equal the charge on the ion
Hydrogen
Usually +1
When bonded to Group I or Group II, becomes -1
Oxygen
Usually -2
O2 is 0
Peroxide’s (H2O2) oxygen atoms are -1
Fluorine
Always -1
Other halogens (Cl, Br, I) are usually -1, except when bonded to oxygen

9. Examples – Find ON for each atom
H2 H =
Fe2O3 Fe = O =
KMnO4 K = Mn = O =
SO42- S = O =
Cr2O72- Cr = O =

10. Worksheet 1 – Assigning Oxidation Numbers
For each element: Hg
FeO F- O2
PbI2
NiO
Al2O3
K2Cr2O7
For bolded elements:
HClO3
SO32-
CaCO3
MnO4-
Na2CO3
PbSO4
KClO3
CrO32-

11. Redox Practice Worksheet
For the following reaction, provide:
Oxidation numbers for all of the elements
Which elements were oxidized and reduced
FeO + Al  Al2O3 + Fe

12. FeO + Al  Al2O3 + Fe

13. 2Na + FeCl2  2NaCl + Fe

14. 2C2H2 + 5O2  4CO2 + 2H2O

15. 2PbS + 3O2  2SO2 + 2PbO