Electron-deficient hydride is/are

Options

A. `BH_(3)`
B. `AIH_(3)`
C. `BeH_(2)`
D. All

Answer

To determine which hydrides are electron-deficient, we need to analyze the valence electrons of the central atom in each hydride and see if they have fewer than 8 electrons in their valence shell. Let's break down the options step by step.

### Step 1: Understand Electron-Deficient Hydrides
Electron-deficient hydrides are those that have less than 8 electrons in the valence shell of the central atom. This typically occurs with elements that have fewer than 4 valence electrons.

### Step 2: Analyze Each Option
#### Option A: BCl3 (Boron Trichloride)
- Boron (B) has an atomic number of 5, meaning it has 3 valence electrons.
- In BCl3, boron forms 3 covalent bonds with chlorine atoms.
- Each bond involves the sharing of 2 electrons, resulting in a total of 6 electrons around boron (3 bonds x 2 electrons per bond = 6 electrons).
- Since 6 < 8, BCl3 is an electron-deficient hydride.

#### Option B: AlH3 (Aluminum Hydride)
- Aluminum (Al) has an atomic number of 13, meaning it has 3 valence electrons.
- In AlH3, aluminum forms 3 covalent bonds with hydrogen atoms.
- Similar to boron, aluminum shares its 3 electrons with hydrogen, resulting in a total of 6 electrons around aluminum (3 bonds x 2 electrons per bond = 6 electrons).
- Since 6 < 8, AlH3 is also an electron-deficient hydride.

#### Option C: BeH2 (Beryllium Hydride)
- Beryllium (Be) has an atomic number of 4, meaning it has 2 valence electrons.
- In BeH2, beryllium forms 2 covalent bonds with hydrogen atoms.
- Each bond involves the sharing of 2 electrons, resulting in a total of 4 electrons around beryllium (2 bonds x 2 electrons per bond = 4 electrons).
- Since 4 < 8, BeH2 is also an electron-deficient hydride.

### Step 3: Conclusion
All three hydrides (BCl3, AlH3, and BeH2) have fewer than 8 electrons in their valence shells, making them electron-deficient hydrides. Therefore, the correct answer is that all of these hydrides are electron-deficient.

### Final Answer
**All of the above (BCl3, AlH3, BeH2) are electron-deficient hydrides.**

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