Question

Which one of the following is the strongest base?
A. $As{{H}_{3}}$
B. $Sb{{H}_{3}}$
C. $P{{H}_{3}}$
D. $N{{H}_{3}}$

Answer 1

Hint: Dependent on the fact that includes the measurement of basicity that is based on the atomic sizes of the central atom and also extent of donation of the lone pair of electrons on it.

Complete step by step answer:
We have come across the chapters in the chemistry that deals with the very basic concepts of acidity and basicity on some of the concepts like Lewis theory, Bronsted acid – base theory and also Lux – Flood concepts.
We shall now see the measurement of basicity according to the trends in the group about basicity and also one of the theories that is Lewis acid – base theory.
- The nitrogen family consists of a lone pair of electrons present on then and the hydrides of this nitrogen family have the basicity on the basis of the group in which the central atom is present.
- As we go down the group, the atomic size of the central atom increases and this in turn diffuses their orbital and therefore, the nucleophilicity of the lone pair will be less dense over bigger atom atoms and this decreases its basicity.
- Now, due to the smaller atomic size of ammonia, the lone pair of electrons is concentrated over smaller region and hence it gets stronger basic property whereas the other three hydrides of this group that is $P{{H}_{3}}$, $Sb{{H}_{3}}$, $As{{H}_{3}}$ will have bigger atomic sizes respectively according to their group number and thus becomes less basic.
- The donation of lone pairs of electrons in ammonia is more compared to the other and therefore, ammonia will be stronger than Lewis base.

Thus, the correct answer is option D. $N{{H}_{3}}$.

Note: The measurement of basicity can be done in other forms too which includes the capacity of the molecule to abstract hydrogen atoms and also based on the solutions of the compounds that are based on the pH of that solution.