Chapter 17.1-17.3 Oxidation & Reduction Methods Revisited

What are the rules for determining the oxidation number of an atom in a compound?

1. Any uncombined element = zero

2. Many atoms or ions have fixed oxidation numbers in compounds:

   1. G1 elements = +1

   2. G2 elements = +2

   3. Fluorine = -1

   4. Hydrogen = +1

      1. Exception: hydrides like NaH where it’s -1

   5. Oxygen = -2

      1. Exception: peroxides where it’s -1 and F₂O (+2)

3. Oxidation number of an element in a monoatomic ion = charge of ion

4. Sum of oxidation numbers in a compound = zero

5. Sum of oxidation numbers in an ion = charge of ion

6. In either a compound or an ion, the more electronegative element is given the negative oxidation number

Involves the loss of electrons; oxidation number increases; half reactions have electrons as products

oxidation

Involves the gain of electrons; oxidation number decreases; half-reactions have electrons as reactants

reduction

Redox reaction gets broken down into _________, one for oxidation and the other for reduction.

half-reactions

What are the steps to balancing half-reactions

1. Assign oxidation numbers

2. Write oxidation & reduction half-reactions, including electrons

3. Balance half-reactions by mass

   1. First balance elements other than H and O

   2. Add H₂O where need O

   3. Add H⁺ where need H

   4. Neutralize H⁺ with OH^- in base to form H₂O (if occurring in basic solution)

4. Balance half-reactions by charge

5. Balance electrons between half-reactions

6. Add half-reactions

The element getting oxidized and reduces something else

reducing agent

The element getting reduced and oxidizes something else

oxidizing agent