Summary of Oxidation and Oxidation Numbers

Reducing and Oxidizing Agents
- Reducing agent: oxidizes and donates electrons.
- Oxidizing agent: is reduced and gains electrons.
Oxidation Numbers
- Definition: Charge an atom would possess if compounds were ionic.
- Elemental substances have an oxidation number of 0.
- Oxidation number of a monoatomic ion equals the ion's charge.
Specific Oxidation States
- Hydrogen:
- +1 with nonmetals (e.g., H₂O)
- -1 with metals (e.g., NaH)
- Oxygen:
- -2 in most compounds
- -1 in peroxides and superoxides
- +2 when combined with Fluorine
- Halogens:
- -1 for F and other halogens (except when combined with oxygen or other halogens).
Sum of Oxidation Numbers
- Total equals the charge on the molecule or ion.
Example Calculation of Oxidation States
- For H₂S:
- H: +1 each; total for 2 H: +2
- Let S charge = x; then, x + 2 = 0, hence x = -2
- For SO₃²⁻:
- O: -2 each; three O contributes -6;
- Set up: -2 = x - 6, hence x = +4
Algebraic Method for Charge Calculation
- Use algebra to calculate oxidation states of compounds based on known oxidation numbers.