IF2- lewis structure contains one iodine atom at the middle position whereas two fluorine atoms at the surrounding position. There are three lone pairs present on the central atom of IF2- lewis structure.
Also, the iodine central atom in IF2- lewis structure violates the octet as it is holding more than 8 electrons in its octet shell.
Follow some steps for drawing the lewis structure of IF2-
1. Count total valence electron in IF2-
As the lewis diagram is all about filling the valence electron around the atoms within a molecule, hence, finds the total valence electron in IF2- molecule.
To count the valence electron in IF2- molecule, look at the periodic group of iodine and fluorine atoms in the periodic table. Since both iodine and fluorine atom belongs to the same periodic group(Group 17), they have the same valence electrons.
⇒ Total number of the valence electrons in iodine atom = 7
∴ Total number of valence electron available for IF2- lewis structure = 7 + 7(2) + 1 = 22 valence electrons [∴ IF2- molecule has one iodine and two fluorine atom with one negative charge ion]
2. Find the least electronegative atom and place it at center
A less electronegative atom is capable to share more electrons, hence, the least electronegative atom takes the middle position in the lewis diagram.
In the case of the IF2- molecule, both iodine and fluorine atoms belong to the same periodic group but “the electronegativity of an element decrease as we down the group”.
Hence, the iodine atom(2.66) is less electronegative than the fluorine atom(3.98), so, place iodine at the central position and fluorine spaced evenly around it.
3. Connect outer atoms to central atom with a single bond
In this step, connect both fluorine atoms to the iodine central atom with the help of a single bond.
Now count the valence electrons we used in the above structure. One single bond means two electrons. In the above structure, we use two single bonds for connecting both side fluorine atoms to the iodine central atom.
Therefore, (2 single bond × 2) = 4 valence electrons we used in the above structure from a total of 22 valence electrons that is available for IF2- lewis structure.
∴ (22 – 4) = 18 valence electrons
So, we are left with 18 valence electrons more.
4. Place remaining valence electrons starting from outer atom first
Now start placing the remaining valence electrons on the outer atom(fluorine) to complete their octet i.e. providing 8 valence electrons in the outer shell of each fluorine atom.
As you see in the above figure, we have placed 6 valence electrons represented as dots around both sides of fluorine atoms. This is because each fluorine atom already shares two valence electrons with the help of a single bond.
Hence, (one single bond means 2 electrons + 6 valence electrons as dots) means a total of 8 valence electrons are present around each fluorine atom, hence, both of them completed their octet comfortably.
Now count the remaining valence electrons. In the above structure, (12 valence electrons represented as dots + 2 single bond that contains 4 electrons) are uses, hence, (12 + 4) = 16 valence electrons are used from total of 22 valence electron available for IF2-.
∴ (22 – 16) = 6 valence electrons
So, we are left with only 6 valence electrons.
5. Complete central atom octet and make covalent bond if necessary
We have 6 remaining valence electrons and iodine is the central atom that needs 8 electrons in its octet to attain stability. But the iodine atom already has 4 electrons in its octet because of two single bonds connected to it.
But iodine atom can expand the octet i.e. having more than 8 valence electrons in the outer shell, this is because iodine is below period two on the periodic table and have an extra d-orbital available hence, it has the ability to expand the octet.
So, put these 6 remaining valence electrons around the iodine central atom.
As we see in the above figure, the iodine central atom gets 10 electrons(6 represented as dot + 2 single bonds) in its outer shell and violates the octet rule. But this is not the issue, some elements can violate the octet to gain stability.
So, both atoms (iodine and fluorine) completed their octet and we use all the total valence electrons that are available for drawing the IF2- lewis structure.
Now we will check the stability of the above structure with the help of a formal charge concept.
6. Check the stability with the help of a formal charge concept
To calculate the formal charge on an atom. Use the formula given below-
First, count the formal charge on the fluorine atom.
For fluorine atom:
⇒ Valence electrons of fluorine = 7
⇒ Nonbonding electrons on fluorine = 6
⇒ Bonding electrons around fluorine(1 single bond) = 2
∴ (7 – 6 – 2/2) = 0 formal charge on both sides fluorine atom.
For iodine atom
⇒ Valence electrons of iodine = 7
⇒ Nonbonding electrons on iodine = 6
⇒ Bonding electrons around iodine (2 single bonds) = 4
∴ (7 – 6 – 4/2) = -1 formal charge on the iodine central atom.
∴ The overall formal charge in IF2- lewis structure is -1 which is equal to the charge on the ion(IF2- molecule has one negative charged ion).
So, the above structure is the most stable, and lastly, put the bracket around both sides of the Iodine difluoride lewis structure and show its negative charged ion.
IF2- lewis structure
The lewis structure for IF2+
For IF2+, we have 20 valence electrons and the central atom iodine has 2 lone pairs and 2 shared pairs.
The molecular geometry of IF2- is linear, this is because the iodine central atom has three lone pairs on an equatorial position and 2 bonded pairs are attached to it.
As per VSEPR theory, the three lone pairs on iodine central atom repel each other as well as adjacent bonded pairs, as a result, the bond pair and lone pair pushed apart from each other and distorted the shape.
∴ The resultant molecular shape of IF2- appears linear.
We can also find the molecular and electron geometry of IF2- with the AXE method.
AXE is the simple generic formula that is based on bonded atom and lone pair on central atom of a molecule.
AXE notation for IF2- molecule:
A denotes the central atom, so, iodine is the central atom, A = Iodine
X represent the bonded atoms to the central atom, as we know, iodine is bonded with two fluorine atoms. Therefore, X = 2
E represent the lone pair on the central atom, as per IF2- lewis structure, iodine has three lone pairs. Hence, E = 3
So, the AXE generic formula for the IF2- molecule becomes AX2E3.
VSEPR theory or chart says, if the central atom of any molecule is attached with two bonded atoms and contains a total of three lone pairs then the molecular shape of that molecule is linear, and electron geometry is trigonal bipyramidal in nature.
Hybridization of IF2-
To find the hybridization of IF2-, just determine the steric number of the central atom.
The steric number can be found by the addition of a lone pair and bonded atom to a central atom.
∴ Steric number of IF2- = (Number of bonded atoms to iodine + Lone pair on iodine central atom)
The iodine central atom is bonded with two fluorine atoms and contains a total of three lone pairs according to the IF2- lewis structure.
∴ Steric number of IF2- = (2 + 3) = 5
Steric number
Hybridization
1
S
2
Sp
3
Sp²
4
Sp³
5
Sp³d
6
Sp³d²
So, we get the Sp3d hybridization for the IF2- molecule for a steric number of five.
Iodine difluoride polarity: is IF2- polar or nonpolar?
A polar molecule has non zero dipole moment and charges are distributed asymmetrical all over the atoms. In nonpolar molecules, charges are the same, hence, all dipole is canceled out.
So, Is IF2- polar or nonpolar? IF2- is nonpolar in nature because its molecular shape is linear that means dipole that is induced because of the difference in electronegativity value of iodine and fluorine atoms are strictly opposite in direction to each other.
“Also, the three lone pairs of electrons on iodine central atom are 120∘ away from each adjacent one, a rotationally-symmetric configuration; so, the lone-pair-bonding-pair repulsions sum to cancel out as well.”
The dipoles that are generated along with the bonds(I-F) will cancel out to give a net dipole moment of zero in all directions irrespective of the difference in electronegativity value between iodine and fluorine.
Hence, the cancellation of dipole and symmetric geometry makes the IF2- nonpolar in nature.
As per the IF2- lewis structure, iodine is the central atom that contains 3 lone pairs and 2 bonded pairs attached to it. These electron pairs (lone pair + bond pair) will repel each other and tried to go far away to minimize the repulsion.
Hence, in all this process, these electron pairs around iodine atom take the position where repulsion between them remains minimum and the final molecular shape of IF2- appears as linear geometry with bond angle 180°.
Also, the generic formula for IF2- is AX2E3 which implies the linear molecular shape and trigonal bipyramidal electron geometry.
Why does the iodine central atom in IF2- lewis structure violate the octet and attain more than 8 electrons?
This is because the iodine atom is below period two on the periodic table and has access to the d-orbital, hence when it becomes necessary, the iodine atom can open its extra d-orbital and attains more than 8 electrons to complete the octet.
Examples of some elements that can expand their octet whenever it’s required – Sulfur, phosphorus, silicon, chlorine, etc.
“Elements in the first 2 periods of the Periodic Table do not have access to the d sublevel and must adhere to the octet rule.”
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
Topblogtenz is a website dedicated to providing informative and engaging content related to the field of chemistry and science. We aim to make complex subjects, like chemistry, approachable and enjoyable for everyone.
