The species, having bonds angle of `120^(@)` is

Options

A. `PH_(3)`
B. `ClF_(3)`
C. `NCl_(3)`
D. `BCl_(3)`

Explanation

To determine which species has a bond angle of 120 degrees, we need to analyze the given options based on their molecular geometry. The bond angle of 120 degrees is characteristic of a trigonal planar geometry, which occurs when the steric number is 3 (i.e., three bond pairs and no lone pairs).

### Step-by-Step Solution:

1. **Identify the Options:**
The given species are:
- PH3
- ClF3
- NCl3
- BCl3

2. **Calculate the Steric Number for Each Species:**
The steric number can be calculated using the formula:
\[ \text{Steric Number} = \frac{(V + M + \text{Charge})}{2} \]
where:
- \( V \) = number of valence electrons of the central atom
- \( M \) = number of monovalent atoms attached
- Charge = charge on the central atom (if any)

3. **Calculate for PH3:**
- Valence electrons (P) = 5
- Monovalent atoms (H) = 3
\[ \text{Steric Number} = \frac{(5 + 3 + 0)}{2} = \frac{8}{2} = 4 \]
This indicates a tetrahedral geometry, not trigonal planar.

4. **Calculate for ClF3:**
- Valence electrons (Cl) = 7
- Monovalent atoms (F) = 3
\[ \text{Steric Number} = \frac{(7 + 3 + 0)}{2} = \frac{10}{2} = 5 \]
This indicates a trigonal bipyramidal geometry, not trigonal planar.

5. **Calculate for NCl3:**
- Valence electrons (N) = 5
- Monovalent atoms (Cl) = 3
\[ \text{Steric Number} = \frac{(5 + 3 + 0)}{2} = \frac{8}{2} = 4 \]
This indicates a tetrahedral geometry, not trigonal planar.

6. **Calculate for BCl3:**
- Valence electrons (B) = 3
- Monovalent atoms (Cl) = 3
\[ \text{Steric Number} = \frac{(3 + 3 + 0)}{2} = \frac{6}{2} = 3 \]
This indicates a trigonal planar geometry.

7. **Conclusion:**
Since BCl3 has a steric number of 3 and exhibits trigonal planar geometry, it has a bond angle of 120 degrees.

### Final Answer:
The species that has a bond angle of 120 degrees is **BCl3**.

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