(i) Electron deficient compounds of hydrogen do not have sufficient number of electrons to form normal covalent bonds. Examples include hydrides of group 13 such as \\\\(\\displaystyle BH_3, AlH_3 \\\\) etc. They exist in polymeric forms such as \\\\(\\displaystyle B_2H_6, Al_2H_6 \\\\). Thus, they make up their deficiency.(ii) Electron precise compounds of hydrogen contain sufficient valence electrons to form covalent bonds. Examples include group 14 hydrides \\\\(\\displaystyle CH_4,SiH_4, GeH_4, SnH_4, PbH_4 \\\\) etc. These compounds have tetrahedral shape.(iii) Electron rich compounds of hydrogen contain excess valence electrons to form covalent bonds.Examples include group 15 and group 17 hydrides such as \\\\(\\displaystyle NH_3, PH_3, HCl, HBr \\\\) etc. These compounds contains lone pairs of electrons.