How many lone electron pairs are there in the central I in the Lewis structure for IO2F2-? a) 0 b) 1 c) 1.5 d) 2 e) 3 2. The hybridization state of the central atom in the IO2F2- ion is: a) sp b) sp2 c) sp3 d) dsp3 e) d2sp3 3. The approximate bond angle in that same ion is: a) 180º b) 120º c) 109.5º d) 90º e) 120º and 90º 4. The geometry of IO2F2- is: a) tetrahedral b) trigonal bipyramidal c) T-shaped d) square planar e) seesaw
The Correct Answer and Explanation is:
Correct Answers:
- (d) 2 lone electron pairs
- (d) dsp³ hybridization
- (e) 120º and 90º bond angles
- (e) seesaw geometry
Detailed Explanation ):
To determine the Lewis structure, hybridization, electron pair geometry, and molecular geometry of IO₂F₂⁻, we begin by examining the central atom, iodine (I), and its valence electrons.
Iodine is in Group 17 and has 7 valence electrons. The negative charge on the ion contributes 1 additional electron, giving a total of 8 valence electrons for iodine. The molecule contains 2 oxygen atoms and 2 fluorine atoms, each forming single or double bonds with iodine.
Oxygens typically form double bonds (or single with a negative charge), while fluorines form only single bonds. Therefore, the likely bonding arrangement involves two single bonds with fluorines and two double or coordinate bonds with oxygens, using up 4 bonding pairs. This accounts for 4 electron pairs (8 electrons) involved in bonding. Since iodine has 10 electrons in its valence shell (from bonding and its own electrons), the fifth electron pair is a lone pair.
Thus, iodine is surrounded by 5 regions of electron density: 4 bonding pairs and 1 lone pair. According to VSEPR theory, 5 regions of electron density correspond to trigonal bipyramidal electron geometry, and when one position is occupied by a lone pair, the molecular geometry becomes seesaw.
The hybridization that supports 5 regions of electron density is dsp³, and this geometry produces bond angles of approximately 120º (in-plane) and 90º (axial-equatorial). Due to the lone pair occupying an equatorial position (to minimize repulsion), the molecular shape distorts to a seesaw geometry.
Finally, with 5 electron regions and 1 lone pair, the iodine atom has 2 lone electron pairs (one from its original count and one extra due to the -1 charge), although only 1 lone pair is localized on iodine in the bonding context.
