question_answer 1)

  The geometry of a complex species can be understood from the knowledge of type of hybridisation of orbitals of central atom. The hybridisation of central atom in \[{{[B{{(OH)}_{4}}]}^{-}}\] and the geometry of the complex are respectively : (a)\[s{{p}^{3}}\], tetrahedral                                                      (b) \[s{{p}^{3}}\], square planar (c) \[s{{p}^{3}}{{d}^{2}}\], octahedral                                                     (d) \[ds{{p}^{2}}\], square planar

Answer:

  (a) Boron has the electronic configuration: \[1{{s}^{2}},2{{s}^{2}}2p_{x}^{1}2p_{y}^{0}2p_{z}^{0}\] Under excited state 2s-orbital is unpaired and one electron is shifted to p-orbital. Now, the hybridisation occurs between one s- and three p-orbitals to give a tetrahedral configuration. \[\underbrace{1{{s}^{2}}2{{s}^{1}}2p_{x}^{1}2p_{y}^{1}2p_{z}^{0}}_{s{{p}^{3}}-hybridisation}\]