Which of the following acts as a ligand but does not have any lone pair of electrons ?

Options

A. `NO_(2)`
B. `NH_(3)`
C. `BF_(3)`
D. `H_(2)O`

Explanation

To solve the question "Which of the following acts as a ligand but does not have any lone pair of electrons?" we will analyze each option provided: NO2, NH3, BF3, and H2O.

### Step 1: Understanding the concept of a ligand
A ligand is defined as an ion or molecule that can donate a pair of electrons to a central atom in a coordination complex. For a substance to act as a ligand, it typically needs to have at least one pair of electrons available for donation.

### Step 2: Analyzing each option

#### Option A: NO2 (Nitrogen Dioxide)
1. **Valence Electrons Calculation**:
- Nitrogen (N) has 5 valence electrons.
- Each Oxygen (O) has 6 valence electrons, and there are 2 O atoms.
- Total = 5 + (2 × 6) = 17 valence electrons.

2. **Structure**:
- In the NO2 molecule, nitrogen forms bonds with both oxygen atoms.
- The nitrogen has one unpaired electron, which is not a lone pair but can still act as a ligand by forming a bond with a central atom.

3. **Conclusion**: NO2 acts as a ligand but does not have any lone pairs of electrons.

#### Option B: NH3 (Ammonia)
1. **Valence Electrons Calculation**:
- Nitrogen has 5 valence electrons.
- Each Hydrogen (H) has 1 valence electron, and there are 3 H atoms.
- Total = 5 + (3 × 1) = 8 valence electrons.

2. **Structure**:
- NH3 has three hydrogen atoms bonded to nitrogen, which has one lone pair of electrons.

3. **Conclusion**: NH3 has a lone pair of electrons, so it cannot be the answer.

#### Option C: BF3 (Boron Trifluoride)
1. **Valence Electrons Calculation**:
- Boron (B) has 3 valence electrons.
- Each Fluorine (F) has 7 valence electrons, and there are 3 F atoms.
- Total = 3 + (3 × 7) = 24 valence electrons.

2. **Structure**:
- In BF3, boron is bonded to three fluorine atoms but has only 6 electrons around it, making it electron deficient.

3. **Conclusion**: BF3 cannot act as a ligand because it cannot donate electrons.

#### Option D: H2O (Water)
1. **Valence Electrons Calculation**:
- Oxygen has 6 valence electrons.
- Each Hydrogen has 1 valence electron, and there are 2 H atoms.
- Total = 6 + (2 × 1) = 8 valence electrons.

2. **Structure**:
- H2O has two hydrogen atoms bonded to oxygen, which has two lone pairs of electrons.

3. **Conclusion**: H2O has lone pairs of electrons, so it cannot be the answer.

### Final Answer
After analyzing all options, the only molecule that acts as a ligand but does not have any lone pairs of electrons is **NO2**.

Thus, the correct answer is **Option A: NO2**.

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