What is the order of basic nature of hydrides of VA group elements?

Options

A. `AsH_(3)gt SbH_(3) gtPH_(3)gt NH_(3)`
B. `NH_(3)> PH_(3) gt AsH_(3) gtSbH_(3)`
C. `NH_(3) gtSbH_(3)gt PH_(3)gt AsH_(3)`
D. `PH_(3) gtNH_(3)gt SbH_(3)gt AsH_(3)`

Answer

To determine the order of basic nature of hydrides of VA group elements (Group 15), we will analyze the hydrides: NH₃ (ammonia), PH₃ (phosphine), AsH₃ (arsine), and SbH₃ (stibine).

### Step-by-Step Solution:

1. **Identify the Hydrides**: The hydrides of the VA group elements are NH₃, PH₃, AsH₃, and SbH₃.

2. **Understand Basic Nature**: The basic nature of a hydride is determined by its ability to donate a lone pair of electrons. A stronger base will have a greater tendency to donate its lone pair.

3. **Consider Atomic Size and Electronegativity**: As we move down the group from nitrogen to antimony:
- The size of the central atom increases.
- The electronegativity of the central atom decreases.

4. **Effect on Lone Pair Donation**:
- With an increase in atomic size, the bond length between the central atom and hydrogen increases. This makes the bond weaker and the lone pair less available for donation.
- A decrease in electronegativity means that the central atom holds onto its electrons less tightly, but the larger size means that the lone pair is less available for donation.

5. **Order of Basicity**:
- NH₃ (ammonia) has the smallest atomic size and highest electronegativity, making it the most basic.
- PH₃ (phosphine) is next, as it has a larger size and lower electronegativity than NH₃.
- AsH₃ (arsine) follows, with even larger size and lower electronegativity.
- SbH₃ (stibine) is the least basic due to the largest size and lowest electronegativity.

6. **Final Order**: Therefore, the order of basic nature of the hydrides is:
- NH₃ > PH₃ > AsH₃ > SbH₃

### Conclusion:
The order of basic nature of the hydrides of VA group elements is NH₃ > PH₃ > AsH₃ > SbH₃.