IO2- Lewis Structure, Characteristics:11 Facts You Should Know

IO2- is an oxyanion of halogen having molar mass 185.91 g/mol. Let us explain in brief about IO2- lewis structure below.

The central atom Iodine is sp3 hybridized along with two pairs of lone pair .The bond angle is smaller than expected due to steric repulsion. IO2- is an oxyanion halogen of Iodine and Iodine bears a negative charge in the IO2- lewis structure.

It is bent shape due to the presence of lone pair. The lone pair-bond pair repulsion makes the geometry of IO2- bent like a water molecule. Let us focus on some important facts about IO2- like, lone pairs, valence electrons, hybridization.

1.    How to draw IO2- lewis structure

We have to follow some basic steps to draw IO2- lewis structure. Let us discuss below how to draw a lewis structure.

Counting the Valence electrons –

We have to count the total valence electrons for the IO2- lewis structure. The valence electrons for Iodine and Oxygen are 7 and 6 as they are group 17th and 16th elements respectively. So, the total number of valence electrons are 7+6+6+1 =20 electrons. One electron is added for extra negative charge.

Choosing the central atom –

Now, we select one atom as the central atom based on size and electronegativity. The size of I is larger than O, so iodine is considered a central atom here. Two O atoms surrounds around the central I.

Satisfying the octet rule –

Every atom in the covalent molecule follows the octet rule. According to this rule, every atom completes valence orbital. So, the electrons that are required to complete octet are 3*8 = 24. Hence, shortage of 24-20 = 4 electrons are satisfied by 4/2 = 2 bonds. So, a minimum of two bonds are required.

Adding multiple bonds –

Now join all the surrounding and terminal atoms with the central atom by the required number of single bonds to make the molecular structure. After connecting all the atoms we have to check whether the valency of all atoms is satisfied or not. If needed then we add multiple bonds between such atoms.

Assigning the lone pairs –

After adding multiple bonds, we assign the lone pairs over the respective atoms if needed. We also add lone pairs over I as well as O atoms.

2.    IO2- lewis structure shape

The molecular shape is dependent on VSEPR theory and the presence of steric crowding of surrounding atoms. Let us understand the shape of IO2- in detail.

IO2- lewis structure shape is not linear. The shape is slighltly bent arround the central atom. IO2- lewis structure is of AX2 type molecule, which is generally adopts linear geometry. But here shape is bent due to lone pairs repulsion.

IO2- Shape

For this reason, the molecule bent its geometry to avoid such repulsion like a water molecule. So, the shape of the IO2- lewis structure is bent. It is an exceptional case of VSEPR theory due to avoiding repulsion. Even the bond angle of the molecule is also changed.

3.    IO2- valence electrons

In the IO2- there are also valence electrons present for I and O separately. Let us calculate total number of valence electrons in the IO2- lewis structure

IO2- has total 20 valence electrons. Those number are the summation of valence electrons of individual atoms. Iodine has seven valence electrons and Oxygen has six valence electrons in their respective outermost orbital. One extra electron is counted for the negative charge present on the molecule.

The electronic configuration of Iodine and Oxygen are [Kr]4d105s25p5 and [He]2s22p4. So, they have seven and six valence electrons in their respective valence orbital. So, total number of valence electrons is 7+6+6+1=20 electrons, as two Oxygen atoms and one negative charge is also present there.

4.    IO2- lewis structure lone pairs

Lone pairs are the non-bonded valence electrons that are present in the outermost orbitals of particular atoms. Let us check the lone pairs of the IO2-.

Iodine has four pairs of lone pair because it has seven valence electrons. Among them three electrons are involved in the bond formation. Again, O has four lone pairs among six valence electrons and two electrons are involved in the bond formation. So, both Iodine and Oxygen contain lone pairs here.

In IO2-, the total number of lone pairs are the summation of lone pairs of I and two O atoms. I contains two pairs of lone pairs and each O atoms contain two pairs of lone pairs. So, the total pairs of lone pairs present over IO2- lewis structure is 2+2+2 = 6 pairs of lone pairs including Iodine and Oxygen atoms.

Know more about Hydrophobic Examples

5.    IO2- lewis structure formal charge

To calculate the formal charge of IO2- lewis structure we assume the same electronegativity of all atoms for O and I. Let us find out the formal charge of IO2-.

The formula we can use to calculate the formal charge, F.C. = Nv – Nl.p. -1/2 Nb.p. where Nv is the number of electrons in the valence shell or outermost orbital, Nl.p is the number of electrons in the lone pair, and Nb.p  is the total number of electrons that are involved in the bond formation only.

We calculate the formal charge individually for Iodine as well as O.

The formal charge over I is, 7-4-(8/4) = -1

The formal charge over O is, 6-4-(4/2) = 0

Hence proved from the calculation of the formal charge of IO2- lewis structure, that iodine has a formal charge value of -1. This inturn suggest that there is a negative charge present over iodide.

6.    IO2- lewis structure angle

The bond angle of IO2- lewis structure is less than 1090 due to its bent shape. Let us find out the reason behind the deviation from its ideal value.

The exact O-I-O bond angle of IO2- is about 1050. The normal bond angle for AX2 type molecule is 1800 if the molecule adopts linear geometry. But here IO2- is not linear so here the bond angle is deviated. The main reason for change in the angle value is to avoid repulsion arround the central atom.

IO2- Bond Angle

In the IO2- structure, there occurs a massive lone pair bond pair repulsion. So, the stability of the molecule is also hampered. In order to avoid this type of repulsion, the molecule changes its geometry as well as bond angle so that it results in a minimum steric repulsion.

7.    IO2- lewis structure octet rule

Every atom in the periodic table follows the octet rule by completing valence shell with a suitable number of electrons. Let us understand how IO2- follows octet rule.

For Iodine, the electronic configuration is [Kr]4d105s25p5. So it needs one more electron to completes its octet. Similarly, for O atom (which is group 16th and belongs to VIA element), has an electronic configuration [He]2s22p4, so it needs two more electrons for fulfiil its octet.

Iodine needs one more electron to complete its octet, so it accumulates negative charge in its 5p orbital and complete its octet. When O formed two bond, it shares two more electrons from the iodine site and complete its 2p orbital by six electrons, and finally complete its octet.

8.    IO2- lewis structure resonance

Delocalization of electron clouds via different canonical form is known as resonance. Now we see how IO2- is stabilizing via its different resonating structures.

There are three possible resonating structures of IO2- lewis structure. But among the three structures, structure I is the most stable and canonical form, as it contains a higher number of covalent bonds, and charge distribution causes no effect in the destabilization.

IO2- Resonating Structures

Structure II also contains the same number of covalent bonds same as structure I but here two negative charges are present over the same molecule which is an unstable factor. Structure III contains the lowest number of covalent bonds. So, its resonance stabilization is lowest.

9.    IO2- hybridization

Different energized orbital cannot make a stable bond, so the atoms undergo hybridization to form hybrid orbital. Let us understand the IO2- hybridization in brief.

The hybridization of central I in the IO2- lewis structure is, ½(7+0+0+1) = 4

Structure     Hybridization value  State of hybridization of central atom         Bond angle
Linear    2sp /sd / pd   1800
Planner trigonal    3sp      1200
Tetrahedral  4sd3/ sp3 109.50
Trigonal bipyramidal 5sp3d/dsp   900 (axial), 1200(equatorial)
Octahedral   6sp3d2/ d2sp3   900
Pentagonal bipyramidal7sp3d3/d3sp3    900,720
IO2- Hybridization

So from the above table, we can conclude that central Iodine is sp3 hybridized here.

From the hybridization and bonding mode of Iodide, it is evident that only sigma bonds are involved in the hybridization. Lone pairs of Iodine are also involved in the hybridization and they are present in the sp3 hybrid orbital.

IO2- Hybridization

10. Is IO2- polar or nonpolar?

Generating dipole moment from electro negative atom to electropositive atom makes a molecule polar. let us see whether IO2- is polar or not.

IO2- is a polar molecule. Due to the asymmetric shape, IO2- is polar, as there is a resultant dipole-moment value present, and charge differences are also observed. The electronegativity difference between O and I atoms are not very high but is enough to generate a dipole moment in the molecule.

Why and How IO2- is polar?

Iodine and Oxygen atoms make dipole-moment within the IO2- molecule to make IO2- polar.

The molecule is polar as the molecule has some resultant dipole moment. The dipole-moment flows from the I to O site and due to the bent shape, the dipole-moment value could not cancel out each other and make the molecule polar.

11. Is IO2- ionic or covalent?

According to Fajan’s rule, none covalent molecule is 100% pure. Every covalent molecule has some % of ionic character. Let us see if IO2- is ionic or covalent.

IO2- is a covalent molecule eventhough there is a presence of negative charge in the molecule. The polarizability of anion is very high but the ionic potential is very less. Therefore, the molecule exhibits very less ionic nature, rather it has a more covalent character.

Why and How IO2- is covalent?

The polarizibility of Iodine is very higher so it can be easily polarizable and make the IO2- covalent.

The covalent nature of a molecule is due to the larger size of Iodine with negative charge makes more polarizable of Iodine anion. It is also depended on the ionic potential of cation as well as the polarizibility of anion. Higher the polarizibility of anion, higher is the covalent character of the anion.


IO2- is a covalent polar molecule, so it has a solubility in water and other polar solvent. Actually, it is a conjugate base rather than a molecule. It is conjugate base Iodous acid.

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