Give an example of a compound in which the oxidation number is fractional.

Answer

To find an example of a compound in which the oxidation number is fractional, let's consider the compound Na₂S₄O₆ (sodium tetrathionate). We will determine the oxidation state of sulfur (S) in this compound step by step.

### Step-by-Step Solution:

1. **Identify the Compound**: We are working with the compound Na₂S₄O₆.

2. **Assign Oxidation States**:
- Sodium (Na) typically has an oxidation state of +1.
- Oxygen (O) typically has an oxidation state of -2.

3. **Set Up the Equation**:
- Let the oxidation state of sulfur be \( x \).
- There are 4 sulfur atoms in the compound, so their total contribution will be \( 4x \).
- The total oxidation state for sodium is \( 2 \times (+1) = +2 \).
- The total oxidation state for oxygen is \( 6 \times (-2) = -12 \).

4. **Write the Overall Charge Equation**:
- The overall charge of the compound is neutral (0).
- Therefore, we can set up the equation:
\[ 4x + 2 - 12 = 0 \]

5. **Solve for \( x \)**:
- Rearranging the equation gives:
\[ 4x - 10 = 0 \]
- Thus,
\[ 4x = 10 \]
\[ x = \frac{10}{4} = \frac{5}{2} \]

6. **Conclusion**:
- The oxidation state of sulfur in Na₂S₄O₆ is \( \frac{5}{2} \), which is a fractional oxidation number.

### Final Answer:
An example of a compound in which the oxidation number is fractional is Na₂S₄O₆, where the oxidation state of sulfur is \( \frac{5}{2} \).

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