`FeSO_(4)` is a very good absorber for `NO`, the new compound formed by this process is found to contain number of unpaired electrons:

Options

A. 4
B. 5
C. 3
D. 6

Explanation

To solve the problem, we will follow these steps:

### Step 1: Identify the Components of the Compound
The compound given is FeSO₄, which dissociates into Fe²⁺ and SO₄²⁻ ions in solution. The iron ion here is in the +2 oxidation state.

**Hint:** Remember that FeSO₄ consists of ferrous ions (Fe²⁺) and sulfate ions (SO₄²⁻).

### Step 2: Determine the Electron Configuration of Iron
The electron configuration of neutral iron (Fe) is:
- Atomic number of Fe = 26
- Electron configuration: [Ar] 4s² 3d⁶

When iron loses two electrons to form Fe²⁺, the electron configuration becomes:
- Fe²⁺: [Ar] 3d⁶

**Hint:** When determining the oxidation state, remember to adjust the electron configuration accordingly.

### Step 3: Analyze the d-Orbitals
For Fe²⁺, the 3d orbitals will have 6 electrons. The distribution of these electrons in the d-orbitals will be:
- 3d: ↑↓ ↑↓ ↑ ↑ ↑

This shows that there are 4 unpaired electrons in the 3d orbitals.

**Hint:** Use Hund's rule to fill the d-orbitals before pairing them.

### Step 4: Consider the Ligands
In the presence of NO (nitric oxide), which acts as a ligand, we need to consider the nature of the ligands. NO is a weak field ligand, which means it does not cause pairing of the d-electrons.

**Hint:** Identify the strength of the ligand to understand its effect on electron pairing.

### Step 5: Determine the Hybridization
In the coordination complex formed with NO, the hybridization can be determined. The coordination number of Fe²⁺ with 5 ligands (NO) is 6, leading to sp³d² hybridization.

**Hint:** The coordination number helps determine the hybridization type.

### Step 6: Count the Unpaired Electrons
Since the weak field ligands do not cause pairing, the number of unpaired electrons remains the same as in the d-orbitals. Therefore, the number of unpaired electrons in the complex is 4.

**Hint:** Count the unpaired electrons in the final configuration after considering ligand effects.

### Final Answer
The number of unpaired electrons in the new compound formed by FeSO₄ absorbing NO is **4**.