Both `N(SiH_(3))_(3) and NH(SiH_(3))_(2)` compounds have trigonal planar skeleton. Incorrect statement about both compounds is :

Options

A. `SiNSi` bond angle in `NH(SiH_(3))_(2)gtSiNSi` bond angle in `N(SiH_(3))_(3))`
B. `N-Si` bond length in `NH(SiH_(3))_(2)gtN-Si` bond length in `N(SiH_(3))_(3))`
C. `N-Si` bond length in `NH(SiH_(3))_(2)ltN-Si` bond length in `N(SiH_(3))_(3))`
D. Back bonding strength in `NH(SiH_(3))_(2)gt` Back bonding strength in `N(SiH_(3))_(3))`

Explanation

To solve the question regarding the incorrect statement about the compounds \(N(SiH_3)_3\) and \(NH(SiH_3)_2\), we will analyze the properties of these compounds step by step.

### Step 1: Identify the Structures
Both compounds have a trigonal planar skeleton.

- **For \(N(SiH_3)_3\)**: The nitrogen atom is bonded to three silicon atoms, each of which is further bonded to three hydrogen atoms. The nitrogen has one lone pair.
- **For \(NH(SiH_3)_2\)**: The nitrogen is bonded to two silicon atoms and one hydrogen atom, with one lone pair on nitrogen.

### Step 2: Analyze Bond Angles
The bond angles in trigonal planar structures are typically around 120 degrees. However, the presence of lone pairs can affect these angles.

- In \(N(SiH_3)_3\), the lone pair on nitrogen will cause some repulsion, potentially increasing the bond angle between the Si-N-Si bonds.
- In \(NH(SiH_3)_2\), the lone pair will also affect the bond angles, but the distribution of bonds is different.

### Step 3: Compare Si-N Bond Lengths
The bond lengths can be influenced by the bond character (single vs. partial double bond character).

- In \(N(SiH_3)_3\), the Si-N bond has a certain bond character due to the presence of three Si-H bonds.
- In \(NH(SiH_3)_2\), the Si-N bond may have a different character due to the fewer Si-H bonds and the presence of a lone pair.

### Step 4: Evaluate the Statements
Now we need to evaluate the statements provided in the question:

1. **Statement A**: The Si-N-Si bond angle in \(NH(SiH_3)_2\) is greater than in \(N(SiH_3)_3\).
- This statement is likely true due to the lone pair repulsion being more pronounced in \(NH(SiH_3)_2\).

2. **Statement B**: The Si-N bond length in \(N(SiH_3)_3\) is greater than in \(NH(SiH_3)_2\).
- This statement is likely false because the presence of more Si-H bonds in \(N(SiH_3)_3\) suggests a stronger bond character, leading to a shorter bond length.

3. **Statement C**: The N-Si bond length in \(NH(SiH_3)_2\) is greater than in \(N(SiH_3)_3\).
- This statement is true as discussed earlier.

4. **Statement D**: The N-Si bond length in \(NH(SiH_3)_2\) is less than in \(N(SiH_3)_3\).
- This statement is likely true as well.

### Conclusion
The incorrect statement about both compounds is **Statement B**: "The Si-N bond length in \(N(SiH_3)_3\) is greater than in \(NH(SiH_3)_2\)."