Q.(a) On the basis of molecular Hydride classify the following compound as electron deficient, electron precise and electron rich hydrides. [2]
B2H6, CH4, H2O and NH3.

The hydrides of group-13 elements, named after the family's first member boron, are called boranes (e.g. diborane, B$_2$H$_6$).

Group 13 (the boron family: B, Al, Ga, In, Tl) elements form electron-deficient hydrides, since each has only 3 valence electrons. Boron itself forms a range of covalent hydrides called boranes, the simplest stable one being diborane, B …

Groups 15, 16, and 17 form covalent, molecular hydrides (like $NH_3$, $H_2O$, HF) — small discrete molecules held together by covalent bonds, as opposed to the ionic hydrides of s-block metals or the metallic/interstitial hydrides of d-block metals.

Step 1 — Recall hydride classification: Hydrogen compounds (hydrides) are broadly classified into three types based on bonding: (i) Ionic (saline) hydrides — formed by highly electropositive s-block metals (e.g. NaH, $CaH_2$), where hydrogen exists as $H^-$;

(ii) Covalent (molecular) hydrides — formed by p-block non-metals;

(iii) Metallic (interstitial) hydrides — formed by d- and f-block metals, where H atoms occupy interstitial sites in the metal lattice.

…