The acidic strength for the hydrides of group 15 follows the order

Options

A. `NH_(3)gtPH_(3)gtAsH_(3)gtSbH_(3)`
B. `NH_(3)ltPH_(3)ltAsH_(3)ltSbH_(3)`
C. `NH_(3)gtPH_(3)gtSbH_(3)gtAsH_(3)`
D. `NH_(3)ltPH_(3)ltSbH_(3)ltAsH_(3)`

Explanation

To determine the acidic strength of the hydrides of Group 15 elements (Nitrogen, Phosphorus, Arsenic, Antimony, and Bismuth), we can follow these steps:

### Step 1: Identify the Hydrides
The hydrides of Group 15 elements are:
- NH₃ (Ammonia)
- PH₃ (Phosphine)
- AsH₃ (Arsine)
- SbH₃ (Stibine)
- BiH₃ (Bismuthine)

### Step 2: Understand Acidic Strength
Acidic strength refers to the ability of a compound to donate a proton (H⁺ ion). The more readily a compound can release H⁺, the stronger the acid it is considered.

### Step 3: Analyze the Size of the Atoms
As we move down the group from Nitrogen to Bismuth, the size of the atoms increases. Larger atoms can stabilize the negative charge of the conjugate base more effectively, making it easier for them to release H⁺ ions.

### Step 4: Order of Acidic Strength
- **NH₃**: Nitrogen is small and holds onto its H⁺ tightly, making it the least acidic.
- **PH₃**: Phosphorus is larger than nitrogen, but it is still not very acidic.
- **AsH₃**: Arsenic is larger than phosphorus, and it can release H⁺ more easily than NH₃ and PH₃.
- **SbH₃**: Antimony is larger than arsenic, making it more acidic than AsH₃.
- **BiH₃**: Bismuth is the largest and can release H⁺ most readily, making it the most acidic.

### Step 5: Final Order of Acidic Strength
Based on the analysis, the order of acidic strength for the hydrides of Group 15 is:
**BiH₃ > SbH₃ > AsH₃ > PH₃ > NH₃**

### Conclusion
Thus, the correct order of acidic strength for the hydrides of Group 15 is:
**BiH₃ > SbH₃ > AsH₃ > PH₃ > NH₃**