why the hydrides of nitrogen is stable while the hydrides of other element of same group are not stable. explain
Stability of hydrides decreases from N to Bi due to the increase in the difference between electronegativities of hydrogen and corresponding element. This leads to polarization of the E-H bond which becomes more ionic than for element in the upper period. At the same time, the stability decreases in order of increasing atomic radius. Since a nucleus of central atom with larger radius attracts bonding electrons weaker, the E-H bond becomes less stable. In addition impact of the inert pair effect increases from N to Bi, when completed electronic sublevels interact with valence orbital decreasing its energy. This leads to low availability of valence electrons and weak E-H interaction.