Question

Which is the strongest Lewis base?
A.$Sb{H_3}$
B.$As{H_3}$
C.$P{H_3}$
D.$N{H_3}$

Answer 1

A Lewis base is considered to be a compound which consists of a lone pair of the electrons which does not participate in the bonding, and can form a coordinate compound on sharing that electron.

Complete step-by-step answer:
In the above question, we can observe that all the above options belong to the same group of hydrides.
Now, nitrogen $N$, phosphorus $P$, arsenic $As$, antimony $Sb$ belongs to the nitrogen family, also known as Group 15. All of their above Atom has one lone pair, so by studying the trend in the group we can find which is the strongest Lewis base.
The major factor that contributes to their different basic strength is their electronegativity and size of an atom. As we go down in a group, the electronegativity of an atom decreases, that is, while going down a group one can easily donate an electron. And as we go down, the size of the atom also increases, causing a decrease in the ability to hold electrons firmly. Now consider the hydride of this atom from going down in the group. It makes it difficult for an atom to accept one proton or ${H^ + }$. Therefore, going down the group, the basic characteristics of hydride decreases.
$N{H_3} > P{H_3} > As{H_3} > Sb{H_3}$
Hence, nitrogen hydride is the strongest Lewis base.
The nitrogen hydride $N{H_3}$ is the strongest Lewis base.

Note: To answer the question which involves the prediction of strongest or weakest amongst some atom or molecules based on a particular property. study the trend in the period or group where the elements in the option are placed; it will give you a brief study of a particular property in that particular group or period.