Question

The structure of $IC{l_2}^ -$ is:
A. Trigonal
B. Octahedral
C. Square planar
D. None of these

Answer 1

We know that the structure can be defined by the VSEPR theory. According to VSEPR theory, $IC{l_2}^ -$ has 7+2+1 = 10 electrons. So, that becomes $\dfrac{{electrons}}{2} = 5$. Therefore, we get to know that the basic geometry is Trigonal Bipyramidal (TBP). As we see there are only 2 bond pairs, and 3 lone pair electrons present. Here, the lone pairs are at an equatorial position which minimizes repulsion. So, the geometry turns out to be linear.

Complete step by step answer:
From the structure of $IC{l_2}^ -$ i.e., iodine dichloride anion has three lone pairs in one plane that are arranged in the shape of a triangle around a central atom. While there are 3 atoms in $IC{l_2}^ -$in a line in the z-plane.
As we know that the structure of $IC{l_2}^ -$is linear with a lone pair. Here, $I$ has 7 electrons and two $Cl$gives two electrons out of which there is one negative charge. Thus, the total number of electrons is 10. So, it makes it trigonal bipyramidal but as there are two three lone pair electrons so it makes it linear in structure with a hybridization of $s{p^3}d$. With $s{p^3}d$ hybridization, we know that it is not trigonal, octahedral, and square planar.

So, the correct answer is Option D.

Note: We know that bond angle is the angle formed between three atoms across at least two bonds. For four atoms bonded together in a chain, the torsion angle is the angle between the plane formed by the first three atoms and the plane formed by the last three atoms. Also, from the structure we know that the bond angle between $Cl - I - Cl$ is ${180^ \circ }$. Then, it is the angle between the lone pairs of electrons or between the lone pair and the chlorine.