Q.What do you understand by

Covalent hydrides of p-block elements (groups 13–17) are classified by comparing the number of valence electrons of the central atom with the number needed to form simple 2-centre-2-electron bonds to all the H atoms and complete an octet.

1. Electron-deficient hydrides: these are hydrides in which the central atom has fewer electrons available than would be needed to form conventional bonds to satisfy an octet using normal 2-electron bonds. Example: diborane, B2H6 — boron (group 13) has only 3 valence electrons, so a simple Lewis structure would leave boron with an incomplete octet (only 6 electrons). Such molecules typically achieve extra stability through unusual bonding, e.g. 3-centre-2-electron ("banana") bridge bonds in B2H6, and behave as strong Lewis acids.
2. Electron-precise hydrides: the central atom has exactly the number of electrons required to form the normal number of 2-electron covalent bonds and complete its octet, with no lone pairs left over. Example: CH4 (methane) — carbon's 4 valence electrons form 4 C–H bond pairs, fully satisfying the octet with nothing left over. Other group 14 hydrides (SiH4, GeH4) are similarly electron-precise. …

For each hydride type, count the central atom's valence electrons versus the electrons needed for a complete octet via normal bond pairs; classify as deficient (too few), precise (exa …

• Mixing up "electron-deficient" with "electron-poor in general" rather than the specific Lewis-structure/octet-completion sense used here. …