Some P Block Elements – NEET UG ChemistryPractice Questions & PYQs

A protonic acid is defined by its ability to directly release a hydrogen ion from its own molecular structure when dissolved in water. Unlike oxoacids such as ${PO}( {OH})_{3}$, ${SO}( {OH})_{2}$, and ${SO}_{2}( {OH})_{2}$, which undergo direct ionization to produce protons, ${B}( {OH})_{3}$ functions instead as a Lewis acid. Upon coordination with a water molecule, the central boron atom utilizes its high polarizing power to withdraw electron density from the water's oxygen atom, ultimately causing the coordinated water molecule to release a proton; since the released ${H}^{+}$ originates from the solvent water molecule rather than the solute itself, ${B}( {OH})_{3}$ is not considered a protonic acid.

The octet rule dictates that stable molecules typically contain eight valence electrons around the central atom, whereas electron-deficient compounds possess fewer. In the molecule ${BCl}_{3}$, the central boron atom undergoes $sp^{2}$ hybridization and forms three covalent bonds with chlorine, which leaves only six electrons in its valence shell. Because this total count is less than the eight required to complete the octet, the molecule is classified as electron-deficient.