Which of the following hydridess is the strongest Lewis base?

Options

A. `PH_(3)`
B. `NH_(3)`
C. `SbH_(3)`
D. `BiH_(3)`

Answer

2

Explanation

All the hydries `(NH_(3)` to`BIH_(3)` behave as Lewis bases as they possess a lone pair of electrons on the central atom. As we move down the group, the size of the central atom increases and the line pair of electrons gets delocalized as it occupies a larger volume. Consequently, the elecrtron density on the central atom decreases causing a decrease in the tendecy to donate a pair of electrons. Hence , the basic strength (sometimes called basicity) decreases in the order:
`NH_(3) gt PH_(3) gt AsH_(3) gt SbH_(3) gt BiH_(3)`