In which of the following cases is the oxidation state of `N` atom wrongly calculated?

Options

A. Compound= `NH_(4)Cl`, Oxidation state= `-3`
B. Compound= `(N_(2)H_(5))_(2)SO_(4)`, Oxidation state= `+2`
C. Compound= `Mg_(3)N_(2)`, Oxidation state= `-3`
D. Compound= `NH_(2)OH`, Oxidation state= `-1`

Explanation

To determine in which case the oxidation state of the nitrogen atom is wrongly calculated, we will analyze each of the given compounds step by step.

### Step 1: Analyze NH4Cl
1. **Write the oxidation state equation**: Let the oxidation state of nitrogen (N) be \( X \).
2. **Identify oxidation states of other elements**:
- Hydrogen (H) has an oxidation state of +1.
- Chlorine (Cl) has an oxidation state of -1.
3. **Set up the equation**:
\[ X + 4(+1) + (-1) = 0 \]
\[ X + 4 - 1 = 0 \]
\[ X + 3 = 0 \implies X = -3 \]
4. **Conclusion**: The oxidation state of nitrogen in NH4Cl is -3. This calculation is correct.

### Step 2: Analyze N2H5SO4
1. **Write the oxidation state equation**: Let the oxidation state of nitrogen (N) be \( X \).
2. **Identify oxidation states of other elements**:
- Hydrogen (H) has an oxidation state of +1.
- Sulfate (SO4) has an overall charge of -2.
3. **Set up the equation**:
\[ 2X + 5(+1) + (-2) = +1 \]
\[ 2X + 5 - 2 = 1 \]
\[ 2X + 3 = 1 \implies 2X = 1 - 3 \implies 2X = -2 \implies X = -1 \]
4. **Conclusion**: The oxidation state of nitrogen in N2H5SO4 is -1. However, it was stated as +2 in the question, which is incorrect.

### Step 3: Analyze Mg3N2
1. **Write the oxidation state equation**: Let the oxidation state of nitrogen (N) be \( X \).
2. **Identify oxidation states of other elements**:
- Magnesium (Mg) has an oxidation state of +2.
3. **Set up the equation**:
\[ 3(+2) + 2X = 0 \]
\[ 6 + 2X = 0 \implies 2X = -6 \implies X = -3 \]
4. **Conclusion**: The oxidation state of nitrogen in Mg3N2 is -3. This calculation is correct.

### Step 4: Analyze NH2OH
1. **Write the oxidation state equation**: Let the oxidation state of nitrogen (N) be \( X \).
2. **Identify oxidation states of other elements**:
- Hydrogen (H) has an oxidation state of +1.
- Oxygen (O) has an oxidation state of -2.
3. **Set up the equation**:
\[ X + 2(+1) + (-2) = 0 \]
\[ X + 2 - 2 = 0 \implies X = 0 \]
4. **Conclusion**: The oxidation state of nitrogen in NH2OH is -1. This calculation is correct.

### Final Conclusion
The oxidation state of nitrogen is wrongly calculated in **N2H5SO4**, where it was stated as +2 instead of the correct value of -1.

### Answer
The case where the oxidation state of the nitrogen atom is wrongly calculated is **B (N2H5SO4)**.