Silane is more reactive than `CH_(4)` towards `Nu^(-)` substitution due to :

Options

A. larger size of Si compared to C which facilitating the attack by nucleophile
B. Polarity of `Si-H` bonds is opposite to that of `C-H` bond
C. Availability of vacant 3d orbitals in case to form the reaction intermediate easily for nucleophilic attack
D. `Si-H` bond energy is lower than that of `C-H` bonds

Explanation

To determine why silane (SiH₄) is more reactive than methane (CH₄) towards nucleophilic substitution, we can analyze several factors that contribute to this difference in reactivity.

### Step-by-Step Solution:

1. **Compare the Structures of SiH₄ and CH₄**:
- Both SiH₄ and CH₄ have a tetrahedral geometry due to sp³ hybridization. However, silicon (Si) is larger than carbon (C), which affects their reactivity.

2. **Consider the Size of the Central Atom**:
- The larger size of silicon compared to carbon allows nucleophiles to approach the silicon atom more easily. In SiH₄, the electron cloud is more spread out, reducing the repulsion experienced by incoming nucleophiles. This facilitates a more favorable attack by the nucleophile.

3. **Analyze the Polarity of the Bonds**:
- The Si-H bond is less polar than the C-H bond. In CH₄, carbon is more electronegative than silicon, resulting in a stronger positive charge on carbon when a nucleophile approaches. In contrast, the silicon atom in SiH₄ is less electronegative, leading to a weaker positive charge. This means that nucleophiles can approach SiH₄ more readily as they are attracted to the positive charge on silicon.

4. **Availability of Vacant Orbitals**:
- Silicon has vacant 3d orbitals that can participate in bonding or accommodate reaction intermediates. This availability allows for easier formation of reaction intermediates during nucleophilic attack, which is not possible in CH₄ since carbon does not have vacant d orbitals.

5. **Bond Energy Considerations**:
- The Si-H bond energy is lower than that of the C-H bond. Lower bond energy means that the Si-H bond can be broken more easily during a nucleophilic substitution reaction. In contrast, the stronger C-H bonds in CH₄ require more energy to break, making CH₄ less reactive towards nucleophiles.

### Conclusion:
Based on these factors, we can conclude that silane (SiH₄) is more reactive than methane (CH₄) towards nucleophilic substitution due to:
- The larger size of silicon facilitating nucleophilic attack.
- The polarity of the Si-H bond being less repulsive to nucleophiles.
- The availability of vacant 3d orbitals in silicon.
- The lower bond energy of Si-H compared to C-H.