What do you expect the nature of hydrides is,if formed by elements of atomic numbers $15$,$19$,$23$,and $44$ with dihydrogen? Compare their behaviour towards water.

(N/A) $(i)$ The element $(Z=15)$ is a $p$-block element,so it forms a covalent hydride,e.g.,$PH_{3}$.
$(ii)$ The element $(Z=19)$ is an $s$-block element,so it forms an ionic hydride,e.g.,$KH$.
$(iii)$ The element $(Z=23)$ is a $d$-block element,so it forms a non-stoichiometric (interstitial) hydride,e.g.,$VH_{1.6}$.
$(iv)$ The element $(Z=44)$ belongs to the $d$-block (Group $8$). Elements of Group $7, 8, 9$ do not form hydrides (this is known as the hydride gap).
Regarding their behaviour towards water: Only the ionic hydride $(KH)$ reacts vigorously with water to produce dihydrogen gas: $KH + H_{2}O \longrightarrow KOH + H_{2}$.