Q.Can phosphorus with outer electronic configuration 3s^2 3p^3 form PH5 ?

Covalent (molecular) hydrides, formed by p-block non-metals, are classified by comparing the number of valence electrons available for bonding with the number required to satisfy the octet rule. Electron-deficient hydrides, typified by Group 13 compounds such as $B_2H_6$, have too few electrons to form conventional two-centre bonds to every neighbouring atom; they behave as Lewis acids, readily accepting electron pairs, and often form unusual bridge bonds to make up the deficiency. Electron-precise hydrides, typified by Group 14 compounds such as $CH_4$ and $SiH_4$, have exactly the electrons needed for a complete octet with all bonds ordinary two-centre two-electron bonds; having neither an empty orbital nor a lone pair available, compounds like $C_nH_{2n+2}$ are chemically inert towards acid–base behaviour and act as neither Lewis acid nor Lewis base. Electron-rich hydrides, typified by Group 15–17 compounds such as $NH_3$, $H_2O$ and $HF$, possess one or more lone pairs beyond the bonding octet, which makes them Lewis bases and lets them act as hydrogen-bon …