In which of the following compounds the transition metal has an oxidation number of `+2`?

Options

A. `Fe_(2)(SO_(4))`
B. `Sc_(2)O_(3)`
C. `V_(2)O_(5)`
D. `NiSO_(4)`

Answer

To determine in which of the given compounds the transition metal has an oxidation number of +2, we will analyze each compound step by step.

### Step 1: Analyze the first compound, Fe2(SO4)3
1. Identify the oxidation state of the sulfate ion (SO4^2-), which is -2.
2. Let the oxidation state of iron (Fe) be x.
3. The compound is neutral, so we can set up the equation:
\[ 2x + 3(-2) = 0 \]
4. Simplifying gives:
\[ 2x - 6 = 0 \implies 2x = 6 \implies x = +3 \]
5. Therefore, the oxidation number of Fe in Fe2(SO4)3 is +3, not +2.

### Step 2: Analyze the second compound, Sc2O3
1. The oxidation state of oxygen (O) is -2.
2. Let the oxidation state of scandium (Sc) be y.
3. The compound is neutral, so we can set up the equation:
\[ 2y + 3(-2) = 0 \]
4. Simplifying gives:
\[ 2y - 6 = 0 \implies 2y = 6 \implies y = +3 \]
5. Therefore, the oxidation number of Sc in Sc2O3 is +3, not +2.

### Step 3: Analyze the third compound, B2O5
1. The oxidation state of oxygen (O) is -2.
2. Let the oxidation state of boron (B) be z.
3. The compound is neutral, so we can set up the equation:
\[ 2z + 5(-2) = 0 \]
4. Simplifying gives:
\[ 2z - 10 = 0 \implies 2z = 10 \implies z = +5 \]
5. Therefore, the oxidation number of B in B2O5 is +5, not +2.

### Step 4: Analyze the fourth compound, NiSO4
1. The oxidation state of the sulfate ion (SO4^2-) is -2.
2. Let the oxidation state of nickel (Ni) be w.
3. The compound is neutral, so we can set up the equation:
\[ w + (-2) = 0 \]
4. Simplifying gives:
\[ w - 2 = 0 \implies w = +2 \]
5. Therefore, the oxidation number of Ni in NiSO4 is +2.

### Conclusion
The correct answer is that the transition metal with an oxidation number of +2 is found in **NiSO4**.