• Rules for Assigning Oxidation Numbers
  

1). Oxidation state of Free elements is  0 e.g. Li, H₂, C etc

2). Oxidation state monatomic ion is the charge Na⁺ = +1, Mg²⁺ = +2, etc

3). Oxidation state of O is -2 in all its compounds exceptions:
a.  peroxides e.g. Na₂O₂; Na-O-O-Na; H₂O₂; H-O-O-H  where Oxygens ox. # = -1
b. superoxides e.g. KO₂ where ox. # = -1/2

4). H is +1 in all its compounds exceptions metal hydrides then = -1 e.g. NaH or MgH₂

5). F is - 1 in all its compounds except in elemental form then ox. # is 0..

6). Alkali metals are always +1; Alkaline Earths are always +2.

7). Sum of oxidation states is zero for neutral compounds, and equal to the overall charge for polyatomic ions.

Reduction- gain of electrons. Look for the oxidation number decreasing.     GER gain electrons reduction

Oxidizing Agents are Reactants that cause oxidation by being reduced (losing electrons; ox. # decreases).

Reducing Agents are Reactants that cause reduction by being oxidized (gaining electrons; ox. # increases).

In the above example Cu²⁺ is the Oxidizing Agent.

In the above example Mg is the Reducing Agents.

Classsify the following as reducing agents or oxidizing agents. 

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