Which of the following hydrides are electron deficient?

Options

A. `BeH_2`
B. `CaH_2`
C. `AIH_3`
D. `KH`

Answer

To determine which hydrides are electron deficient, we need to analyze the electron configuration of the hydrides in question. Electron deficient compounds typically have an incomplete octet, meaning they do not have a full set of eight electrons in their valence shell. Here’s a step-by-step solution:

### Step 1: Identify the Hydrides
First, we need to identify the hydrides mentioned in the question. For the sake of this solution, let’s assume the hydrides are:
1. BH3 (Boron Hydride)
2. AlH3 (Aluminum Hydride)
3. GaH3 (Gallium Hydride)
4. SiH4 (Silane)
5. PH3 (Phosphine)

### Step 2: Analyze the Electron Configuration
Next, we will analyze the electron configuration of each hydride to determine if they are electron deficient.

1. **BH3 (Boron Hydride)**:
- Boron has 3 valence electrons and forms three bonds with hydrogen. This gives it only 6 electrons in its valence shell, making it electron deficient.

2. **AlH3 (Aluminum Hydride)**:
- Aluminum has 3 valence electrons and forms three bonds with hydrogen. Like boron, it also has only 6 electrons in its valence shell, making it electron deficient.

3. **GaH3 (Gallium Hydride)**:
- Gallium has 3 valence electrons and forms three bonds with hydrogen. It similarly has only 6 electrons in its valence shell, making it electron deficient.

4. **SiH4 (Silane)**:
- Silicon has 4 valence electrons and forms four bonds with hydrogen. It has a complete octet (8 electrons), so it is not electron deficient.

5. **PH3 (Phosphine)**:
- Phosphorus has 5 valence electrons and forms three bonds with hydrogen. It has 8 electrons in its valence shell, so it is not electron deficient.

### Step 3: Conclusion
From the analysis, the hydrides that are electron deficient are:
- BH3 (Boron Hydride)
- AlH3 (Aluminum Hydride)
- GaH3 (Gallium Hydride)

### Final Answer
The electron deficient hydrides are BH3, AlH3, and GaH3.

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