What do you understand by (i) electron-deficient, (ii) electron-precise, and (iii) electron-rich compounds of hydrogen? Provide justification with suitable examples.
1. Electron deficient hydrides are referred to those hydrides which contains deficit of electrons after the hydrogen bonding has been formed that is the octet is partially filled after the bond formation.Examples of such hydrides include the hydrides of Group 13 elements. These hydrides cannot be represented by simple Lewis structures and also they have tendency to accept electrons. 2. Electron precise hydride is referred to those class of hydrides in which the octet is completely filled. For example- CH4 
3. Electron rich hydride is referred to those class of hydrides which contains more electrons then actually needed to from the octet. Such hydride has the tendency to lose the extra electrons to form positive radicals. For example- NH3 