Which is least basic ? `SbH_(3), PH_(3), NH_(3), AsH_(3)` ?

Explanation

To determine which compound is the least basic among SbH₃ (stibine), PH₃ (phosphine), NH₃ (ammonia), and AsH₃ (arsine), we can analyze the basicity of these compounds based on their electron density and the size of the central atom.

### Step-by-Step Solution:

1. **Understanding Basicity**: Basicity refers to the ability of a compound to donate a pair of electrons. In the context of hydrides of group 15 elements, the basicity is influenced by the electron density around the central atom.

2. **Group Trend**: As we move down the group from nitrogen (N) to antimony (Sb), the size of the central atom increases. This increase in size leads to a decrease in electron density because the outer electrons are farther from the nucleus.

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