Question

Which of the following has a distorted tetrahedral shape?
A. \[Si{H_4}\]
B. \[CC{l_4}\]
C. \[C{H_4}\]
D. \[CHC{l_3}\]

Answer 1

Hint: In options A, B, and C same atoms are bonded to the central atom whereas in option D different atoms are bonded to the central atom. Similar atoms contain a similar number of valence electrons.

Complete Step by Step Solution:
The molecular geometry of a chemical compound is an arrangement of atoms of a molecule in a three-dimensional space.

In a tetrahedral geometry, the central atom is bonded to four other substituents present at the corners of the tetrahedron.

Silane(\[Si{H_4}\]), carbon tetrachloride (\[CC{l_4}\]), methane(\[C{H_4}\]) and chloroform (\[CHC{l_3}\]) all have tetrahedral shape.
In silane, methane and carbon tetrachloride are the same atoms attached to the central atom. Due to this, they have the same number of electrons so the electron-electron repulsion will be identical in all the atoms and hence no distortion will be observed.
In chloroform, one hydrogen atom and three chlorine atoms are attached to the central carbon atom. Therefore, the chlorine will have more electrons which will cause more repulsion. The size of chlorine is more than hydrogen, so the bond angle of Cl-C-Cl will be higher than 109 degrees and the bond angle of Cl-C-H will be lesser than 109 degrees. This will result in a distorted tetrahedron.
Therefore, \[CHC{l_3}\] has a distorted tetrahedral shape. Thus, option (D) is correct.

Note: To determine the molecule's shape, one should know about the Lewis electron-dot structure. Lewis electron dot structure does not determine the shape of molecules, but it helps in predicting the shape of the molecule. The Lewis structure helps to identify the lone pairs and bond pairs and along with valence-shell electron pair repulsion theory (VSEPR), molecular geometry is determined.