Calculate the oxidation number of the underlined atom in the following ions.
`ul(S)O_(4)^(2-),[ul(Cr)(H_(2)O)_(6)]^(3+),[ul(Fe)(CN)_(6)]^(3-),CrO_(4)^(2-),BrO_(3)^(-)`

Explanation

To calculate the oxidation number of the underlined atoms in the given ions, we will follow a systematic approach for each ion.

### Step-by-Step Solution:

1. **For \( \text{SO}_4^{2-} \) (Sulfur)**:
- Let the oxidation number of sulfur (S) be \( x \).
- Each oxygen (O) has an oxidation number of -2. Since there are 4 oxygen atoms, the total contribution from oxygen is \( 4 \times (-2) = -8 \).
- The overall charge of the sulfate ion is -2.
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