The pair having similar geometry is

Options

A. `PCl_3,NH_3^`
B. `BeCl_2,H_2O`
C. `CH_4," CC"l_4`
D. `IF_5,PH_5`

Answer

To solve the question regarding which pair of compounds has similar geometry, we will analyze the hybridization and geometry of each compound listed in the options.

### Step-by-step Solution:

1. **Identify the first pair: PCl3 and NH3**
- **PCl3:**
- Valence electrons of phosphorus (P) = 5
- Number of monovalent chlorine atoms = 3
- No charge
- Steric number = \( \frac{1}{2} \left( 5 + 3 - 0 + 0 \right) = \frac{8}{2} = 4 \)
- Hybridization = sp³
- Geometry = Trigonal pyramidal

- **NH3:**
- Valence electrons of nitrogen (N) = 5
- Number of monovalent hydrogen atoms = 3
- No charge
- Steric number = \( \frac{1}{2} \left( 5 + 3 - 0 + 0 \right) = \frac{8}{2} = 4 \)
- Hybridization = sp³
- Geometry = Trigonal pyramidal

**Conclusion:** Both PCl3 and NH3 have similar geometry (trigonal pyramidal).

2. **Identify the second pair: BCl2 and H2O**
- **BCl2:**
- Valence electrons of boron (B) = 3
- Number of monovalent chlorine atoms = 2
- No charge
- Steric number = \( \frac{1}{2} \left( 3 + 2 - 0 + 0 \right) = \frac{5}{2} = 2.5 \) (round down to 2)
- Hybridization = sp
- Geometry = Linear

- **H2O:**
- Valence electrons of oxygen (O) = 6
- Number of monovalent hydrogen atoms = 2
- No charge
- Steric number = \( \frac{1}{2} \left( 6 + 2 - 0 + 0 \right) = \frac{8}{2} = 4 \)
- Hybridization = sp³
- Geometry = Bent

**Conclusion:** BCl2 and H2O have different geometries (linear vs bent).

3. **Identify the third pair: CH4 and CCl4**
- **CH4:**
- Valence electrons of carbon (C) = 4
- Number of monovalent hydrogen atoms = 4
- No charge
- Steric number = \( \frac{1}{2} \left( 4 + 4 - 0 + 0 \right) = \frac{8}{2} = 4 \)
- Hybridization = sp³
- Geometry = Tetrahedral

- **CCl4:**
- Valence electrons of carbon (C) = 4
- Number of monovalent chlorine atoms = 4
- No charge
- Steric number = \( \frac{1}{2} \left( 4 + 4 - 0 + 0 \right) = \frac{8}{2} = 4 \)
- Hybridization = sp³
- Geometry = Tetrahedral

**Conclusion:** Both CH4 and CCl4 have similar geometry (tetrahedral).

4. **Identify the fourth pair: IF5 and PH5**
- **IF5:**
- Valence electrons of iodine (I) = 7
- Number of monovalent fluorine atoms = 5
- No charge
- Steric number = \( \frac{1}{2} \left( 7 + 5 - 0 + 0 \right) = \frac{12}{2} = 6 \)
- Hybridization = sp³d²
- Geometry = Octahedral

- **PH5:**
- Valence electrons of phosphorus (P) = 5
- Number of monovalent hydrogen atoms = 5
- No charge
- Steric number = \( \frac{1}{2} \left( 5 + 5 - 0 + 0 \right) = \frac{10}{2} = 5 \)
- Hybridization = sp³d
- Geometry = Trigonal bipyramidal

**Conclusion:** IF5 and PH5 have different geometries (octahedral vs trigonal bipyramidal).

### Final Answer:
The pairs with similar geometry are:
- Option 1: PCl3 and NH3 (Trigonal pyramidal)
- Option 3: CH4 and CCl4 (Tetrahedral)