What do you understand by (i) electron-deficient, (ii) electron-precise, (iii) electron-rich compounds |of hydrogen ? Provide justification with suitable examples
Compounds of hydrogen with other elements are called hydrides. They are (i) electron-deficient, (ii) electron-predse and (iii) electron rich hydrides.
(i) An electron-deficient hydride has very few elec¬trons for writing its conventional Lewis structure. Diborane (${{B}{2}}$${{H}{6}}$) is an example. In fact all elements of group 13 will form electron-defident compounds. They ad as Lewis adds, i.e., electron acceptors.
(ii) Electron-precise compounds have the required number of electrons to write their conventional Lewis structures. Methane (C${{H}{4}}$), ethane (${{C}{2}}$${{H}{6}}$) are examples of electron-predse compounds. In fact, all elements of group 14 form such compounds which are tetrahedral in geometry.
(iii) Electron-rich hydrides have excess of electrons which are present as lone pairs. Elements of group 15-17 form such compound. (N${{H}{3}}$ has one lone pair, ${{H}_{2}}$0 has two and HF has three lone pairs of electrons). They will behave as Lewis bases, i.e., electron-donors.