Question

In which of the following pair both species have same Cl-x-Cl bond angle?
•CCl₄ , SiCl₄
•POCl₃ , SO₂Cl₂
•BCl₃ , AlCl₃
And why??

Answer 1

CCl4 and SiCl4 Both form tetrahedral geometry in 3D. Since the central atom has no lone pairand all the bonds are sigma bonds, there is no distortion in the Cl-X-Cl angle. For both the molecules the Hybridisation is sp3 and the bond angle is 109.5 degress.
Similarly for BCl3 and AlCl3, the hybridisation is sp2 and the bond angle remains 120 degrees.

For POCl3 and SO2Cl2, The geometrical structure in 3D is different because the hybridisation for POCl3 is also sp3 but due to a double bond with oxygen,there will be little distortion(which is caused by the pi electron cloud on interaction with the sigma bonds), which causes the bond angle to be around 108 to 109 degrees.For SO2Cl2, also the hybridisation is sp3, but there are 2 double bonds with oxygen that causes distortion to the tetrahedron formed and reduces the bond angle to 107 degrees.