11th Class Chemistry The p-Block Elements-I

  • question_answer 68)   Draw the structures of \[BC{{l}_{3}},N{{H}_{3}}\] and\[AlC{{l}_{3}}\] (dimer).


      Structure of\[\mathbf{BC}{{\mathbf{l}}_{\mathbf{3}}}\]: In \[BC{{l}_{3}}\] molecule, the boron atom is in\[s{{p}^{2}}\] -hybrid state. Thus, it has planar triangular structure. Structure of\[\mathbf{N}{{\mathbf{H}}_{\mathbf{3}}}\]: In \[N{{H}_{3}}\] molecule, the nitrogen atom is in \[s{{p}^{3}}\]-hybrid state. Thus, it has tetrahedral structure having one hybrid orbital with a lone pair of electrons. The actual shape of the molecule is pyramidal. The bond angle is\[107.5{}^\circ \]. This is less than the expected angle of\[{{109}^{{}^\circ }}28\]? due to repulsion between lone pair present on nitrogen atom and bonded      pairs of electrons.                       Structure of \[AlC{{l}_{3}}\] (dimer):                 Al atom undergoes \[s{{p}^{2}}\] -hybridisation for planar triangular structure. However, to achieve more stability the vacant    p-orbital of Al-atom forms a coordinate bond with one of the chlorine atom of the other molecule forming a dimer.  

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