12th Class Chemistry The p-block Elements-II / p-ब्लॉक तत्व-II Question Bank 11th CBSE Chemistry The P-Block Elements

  • question_answer
    Why \[N{{(C{{H}_{3}})}_{3}}\] is pyramidal but \[N{{(Si{{H}_{3}})}_{3}}\] is planar?

    Answer:

                    In \[N{{(C{{H}_{3}})}_{3}},\,N\] is \[s{{p}^{3}}\]-hybridized with one lone pair of electrons and hence \[N{{(C{{H}_{3}})}_{3}}\] is pyramidal. In \[N{{(Si{{H}_{3}})}_{3}},\]Si is \[s{{p}^{3}}\]-hybridized and forms three \[\sigma \]-bonds with H and fourth with the N-atom. Further due to the presence of d-orbitals, Si has a strong tendency to form  \[p\pi -d\pi \]double bond with N-atom. For this to occur, N must be \[s{{p}^{2}}\]-hybridized so that the p-orbital on N containing the lone pair of electrons can overlap with the empty d-orbital on Si as shown in Fig. 11.14, page 11/26. As a result, \[N{{(Si{{H}_{3}})}_{3}}\] is planar.


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