The Lewis dot diagram for iodite (IO2-) is given below. Using your VSEPR information, determine the most likely molecular geometry (shape) for iodite.
The Correct Answer and Explanation is :
The molecular geometry of iodite (IO₂⁻) is angular (or bent), with a bond angle of approximately 111°.
Explanation:
To determine the molecular geometry, we will follow these steps:
- Lewis Structure:
The Lewis structure of iodite (IO₂⁻) consists of an iodine atom bonded to two oxygen atoms. The iodine atom has one lone pair, and each oxygen atom has two lone pairs. The negative charge is placed on one of the oxygen atoms. This structure follows the octet rule, with iodine having more than 8 valence electrons due to its position in the periodic table (it can accommodate an expanded octet). - Electron Domain Count:
The VSEPR (Valence Shell Electron Pair Repulsion) theory helps us predict the molecular shape by considering electron domains (regions where electrons are likely to be found). In the IO₂⁻ ion, iodine is surrounded by:
- Two bonding regions (the two O-I bonds),
- One lone pair of electrons on the iodine atom. This results in three regions of electron density (two bonding pairs and one lone pair).
- Electron Domain Geometry:
With three regions of electron density, the electron domain geometry is trigonal planar according to VSEPR theory. However, the lone pair on iodine will affect the molecular geometry. - Molecular Geometry:
The lone pair on iodine will repel the bonding pairs of electrons, causing the bonding regions to spread out and adopt a bent or angular shape. The lone pair occupies space but does not contribute to the bonding geometry directly. Therefore, the molecular shape is not trigonal planar but bent. - Bond Angles:
The ideal bond angle for a trigonal planar geometry is 120°, but the presence of the lone pair reduces the bond angle to around 111° due to the lone pair’s repulsion on the bonding pairs.
Thus, based on the VSEPR theory and the presence of a lone pair, the molecular geometry of IO₂⁻ is bent, with a bond angle of about 111°.