Chemical Bonding and Molecular Structure - Result Question 73
####75. The $AsF_5$ molecule is trigonal bipyramidal. The hybrid orbitals used by the As atom for bonding are
(a) $d _{x^{2}-y^{2}}, d _{z^{2}}, s, p_x, p_y$
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(b) $d _{x y}, s, p_x, p_y, p_z$
(c) $s, p_x, p_y, p_z, d _{z^{2}}$
(d) $d _{x^{2}-y^{2}}, s, p_x, p_y, p_z$
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Solution:
- (c) The electronic configuration of As is
$ As=1 s^{2} 2 s^{2} 2 p^{6} \underbrace{3 s^{1} 3 p_x{ }^{1} 3 p_y{ }^{1} 3 p_z{ }^{1} 3 d^{1}} _{\downarrow s p^{3} d \text{ hybridisation }} $
So, the hybrid orbitals used by As atom in $AsF_5$ molecule are $s, p_x, p_y, p_z, d_z{ }^{2}$.
In the formation of a stable trigonal pyramid, the two axial bonds above and below the equatorial xy-plane have to be equally strong. Thus, the $d_z{ }^{2}$ orbital is used.
