Draw electron dot structures of (i) `NH_(3)` (ii) `PCl_(5)` (iii) `C_(2)H_(2).`

Answer

To draw the electron dot structures for the compounds \(NH_3\), \(PCl_5\), and \(C_2H_2\), follow these steps:

### Step 1: Draw the Electron Dot Structure for \(NH_3\) (Ammonia)

1. **Count the Valence Electrons**:
- Nitrogen (N) has 5 valence electrons.
- Each Hydrogen (H) has 1 valence electron. Since there are 3 H atoms, that gives us \(3 \times 1 = 3\) electrons.
- Total = \(5 + 3 = 8\) valence electrons.

2. **Arrange Atoms**:
- Place Nitrogen in the center and surround it with 3 Hydrogen atoms.

3. **Form Bonds**:
- Nitrogen will form single bonds with each Hydrogen atom. Each bond consists of 2 electrons.
- This uses up \(3 \times 2 = 6\) electrons.

4. **Distribute Remaining Electrons**:
- There are \(8 - 6 = 2\) electrons left, which will be placed as a lone pair on Nitrogen.

5. **Final Structure**:
- The final structure shows Nitrogen with one lone pair and three single bonds to Hydrogen atoms.

### Step 2: Draw the Electron Dot Structure for \(PCl_5\) (Phosphorus Pentachloride)

1. **Count the Valence Electrons**:
- Phosphorus (P) has 5 valence electrons.
- Each Chlorine (Cl) has 7 valence electrons. Since there are 5 Cl atoms, that gives us \(5 \times 7 = 35\) electrons.
- Total = \(5 + 35 = 40\) valence electrons.

2. **Arrange Atoms**:
- Place Phosphorus in the center and surround it with 5 Chlorine atoms.

3. **Form Bonds**:
- Phosphorus will form single bonds with each Chlorine atom. Each bond uses 2 electrons.
- This uses up \(5 \times 2 = 10\) electrons.

4. **Distribute Remaining Electrons**:
- There are \(40 - 10 = 30\) electrons left. Each Chlorine atom needs 6 more electrons to complete its octet.
- Distribute these 30 electrons (6 for each Cl) around the Chlorine atoms.

5. **Final Structure**:
- The final structure shows Phosphorus with 5 single bonds to Chlorine atoms, and each Chlorine has 3 lone pairs.

### Step 3: Draw the Electron Dot Structure for \(C_2H_2\) (Acetylene)

1. **Count the Valence Electrons**:
- Each Carbon (C) has 4 valence electrons. Since there are 2 C atoms, that gives us \(2 \times 4 = 8\) electrons.
- Each Hydrogen (H) has 1 valence electron. Since there are 2 H atoms, that gives us \(2 \times 1 = 2\) electrons.
- Total = \(8 + 2 = 10\) valence electrons.

2. **Arrange Atoms**:
- Place the two Carbon atoms in the center and surround them with 2 Hydrogen atoms.

3. **Form Bonds**:
- Carbon atoms will form a triple bond with each other (using 6 electrons) and single bonds with each Hydrogen atom (using 2 electrons).
- This uses up \(6 + 2 = 8\) electrons.

4. **Distribute Remaining Electrons**:
- There are \(10 - 8 = 2\) electrons left, which are used to complete the bonds.

5. **Final Structure**:
- The final structure shows two Carbon atoms connected by a triple bond and each Carbon connected to one Hydrogen atom.

### Summary of Structures:
- **\(NH_3\)**: Nitrogen with 3 single bonds to Hydrogen and 1 lone pair.
- **\(PCl_5\)**: Phosphorus with 5 single bonds to Chlorine, each Chlorine has 3 lone pairs.
- **\(C_2H_2\)**: Two Carbon atoms connected by a triple bond, each with a single bond to a Hydrogen atom.