question_answer 1)

What do you understand by (i) electron deficient (ii) electron precise and (iii) electron rich compounds of hydrogen? Provide justification with suitable examples.

Answer:

(i) The hydrides which do not possess sufficient number of valence electrons to form normal covalent bonds, are termed electron deficient hydrides. Examples are the hydrides of group 13 such as\[B{{H}_{3}},Al{{H}_{3}}\], etc. They generally exist in polymeric forms. (ii) The hydrides which possess exact-number of electrons to form covalent bonds are termed electron precise hydrides. Examples are the hydrides of group 14 such as \[C{{H}_{4}},Si{{H}_{4}},Ge{{H}_{4}}\], etc. (iii) The hydrides which have lone pair or pairs of electrons, i.e., have more electrons than required to form normal covalent bonds are termed electron rich hydrides. Examples are the hydrides of group 15, 16 and 17 such as \[N{{H}_{3}},{{H}_{2}}O,HF\], etc.