Question

What is the shape of $I{Br_{2}}^{-}$ ion?
A. Linear
B. Bent shape with bond angle of about 90°
C. Bent shape with bond angle of about 109°
D. Bent shape with bond angle of about 120°

Answer 1

Hint: The lewis structure is based on the concept of octet rule as the electron shared by each atom should have 8 electrons in its outermost shell.

Complete step by step answer: The following steps are used in lewis structure of any molecule:
-First the skeletal structure for the given molecule is drawn then the total number of valence electrons for atoms present in the molecule is determined.
-In the next step subtract the electron present in the total number of present bonds in the skeletal structure of the molecule (and remember that each bond contains two electrons).
-In the last step ,the electrons which we get after subtraction are equally distributed such that each atom contains eight electrons in its valence shell.
\[I{Br_{2}}^{-}\] ​​ molecule has two bond pairs and three lone pairs. According to bent rule, for \[sp{}^\text{3}d\] hybridisation all lone pairs should be in an equatorial position so as to minimize lone pair- lone pair repulsion, if all 3 lone pairs in \[I{Br_{2}}^{-}\] are placed at the equatorial position then both Br will be along with the axial position, so it will be linear structure(as all atoms lie in the same line)
So, the correct answer is “Option A”.

Note: Bent's Rule describes and explains the relationship between the orbital hybridization of central atoms in molecules and the electro-negativities of substituents.
-We can determine the structure of the molecule through VSEPR also
-The following steps must be followed in order to decide the shape of a molecule.
-The least electronegative atom must be selected as the central atom (since this atom has the highest ability to share its electrons with the other atoms belonging to the molecule).
-The total number of electrons belonging to the outermost shell of the central atom must be counted.
-The total number of electrons belonging to other atoms and used in bonds with the central atom must be counted.
-These two values must be added in order to obtain the valence shell electron pair number or the VSEPR number.