Which of the following is an electron deficient compound?

Options

A. `NH_(3)`
B. `PH_(3)`
C. `BCl_(3)`
D. `AsH_(3)`

Explanation

To determine which of the given compounds is an electron deficient compound, we will analyze the electron configuration and the number of valence electrons for each compound. The compounds we are considering are NS3 (Nitrogen sulfide), PS3 (Phosphorus sulfide), BCl3 (Boron trichloride), and SiH3 (Silane).

### Step-by-Step Solution:

1. **Analyze NS3 (Nitrogen Sulfide):**
- Nitrogen (N) has 5 valence electrons.
- Each sulfur (S) has 6 valence electrons, and there are 3 sulfur atoms.
- Total valence electrons = 5 (from N) + 3 × 6 (from S) = 5 + 18 = 23 electrons.
- In NS3, nitrogen forms three single bonds with sulfur, using 3 of its electrons. This leaves nitrogen with 2 lone pairs (4 electrons) and 3 bond pairs (6 electrons).
- Total around nitrogen = 4 (lone pair) + 6 (bonding) = 8 electrons.
- **Conclusion**: NS3 is not electron deficient.

2. **Analyze PS3 (Phosphorus Sulfide):**
- Phosphorus (P) has 5 valence electrons.
- Each sulfur (S) has 6 valence electrons, and there are 3 sulfur atoms.
- Total valence electrons = 5 (from P) + 3 × 6 (from S) = 5 + 18 = 23 electrons.
- In PS3, phosphorus forms three single bonds with sulfur, using 3 of its electrons. This leaves phosphorus with 1 lone pair (2 electrons) and 3 bond pairs (6 electrons).
- Total around phosphorus = 2 (lone pair) + 6 (bonding) = 8 electrons.
- **Conclusion**: PS3 is not electron deficient.

3. **Analyze BCl3 (Boron Trichloride):**
- Boron (B) has 3 valence electrons.
- Each chlorine (Cl) has 7 valence electrons, and there are 3 chlorine atoms.
- Total valence electrons = 3 (from B) + 3 × 7 (from Cl) = 3 + 21 = 24 electrons.
- In BCl3, boron forms three single bonds with chlorine, using all 3 of its electrons. Boron has no lone pairs.
- Total around boron = 0 (lone pair) + 6 (bonding) = 6 electrons.
- **Conclusion**: BCl3 is electron deficient because it has only 6 electrons instead of the required 8 for a complete octet.

4. **Analyze SiH3 (Silane):**
- Silicon (Si) has 4 valence electrons.
- Each hydrogen (H) has 1 valence electron, and there are 3 hydrogen atoms.
- Total valence electrons = 4 (from Si) + 3 × 1 (from H) = 4 + 3 = 7 electrons.
- In SiH3, silicon forms three single bonds with hydrogen, using 3 of its electrons. This leaves silicon with 1 lone pair (2 electrons) and 3 bond pairs (6 electrons).
- Total around silicon = 2 (lone pair) + 6 (bonding) = 8 electrons.
- **Conclusion**: SiH3 is not electron deficient.

### Final Answer:
The electron deficient compound among the options is **BCl3 (Boron Trichloride)**.