The exact oxidation number of oxygen in potassium superoxide (KO2) is -1/2.
Determining Oxidation States in KO2
To ascertain the oxidation state of an element within a compound, we apply fundamental rules of chemistry. Potassium (K), an alkali metal, consistently exhibits an oxidation state of +1 in its compounds. This is because it possesses only one valence electron, which it readily donates to form a cation.
KO2 itself is a neutral chemical compound. This crucial fact means that the algebraic sum of the oxidation states of all the atoms within it must equal zero.
Step-by-Step Calculation
The oxidation state of oxygen in KO2 can be determined through a straightforward calculation:
- Assign known oxidation states: Potassium (K) has a known oxidation state of +1.
- Define unknown oxidation state: Let the oxidation number of a single oxygen atom be represented by the variable x.
- Account for multiple atoms: Since the chemical formula is KO2, there are two oxygen atoms. Their combined contribution to the total oxidation state will be 2 multiplied by x (i.e., 2x).
- Formulate the equation for neutrality: For a neutral compound, the sum of the oxidation states of all constituent atoms must be zero. Therefore, we can write the equation:
(Oxidation state of K) + (Total oxidation state of O2) = 0 - Substitute values into the equation:
(+1) + (2x) = 0 - Solve for x:
2x = -1
x = -1/2
Summary of Oxidation Numbers in KO2
The calculated oxidation states for each element in KO2 are as follows:
| Element | Oxidation Number |
|---|---|
| Potassium (K) | +1 |
| Oxygen (O) | -1/2 |
This unique oxidation state of -1/2 for oxygen is characteristic of compounds known as superoxides. In most common compounds (oxides), oxygen typically carries an oxidation state of -2, while in peroxides, it is -1. The superoxide ion, O₂⁻, is responsible for this distinct oxidation state.
