IF3 or Iodine trifluoride is a yellow solid and is categorized as an interhalogen compound. It is highly unstable and decomposes above the temperature of -28 degrees Celsius.
The molar mass of IF3 is 183.9 g/mol. IF3 can be prepared using two methods:-
1. F2 + I2 ——> IF3 at −45 °C in CCl3F.
2. At low temperatures, the fluorination reaction is used.
I2 + 3XeF2 ——> 2IF3 + 3Xe
Now let us move on to the important aspects of IF3 ie; lewis structure, molecular geometry, hybridization, etc.
IF3 Lewis Structure
Before we begin to learn the steps for drawing Lewis structure let’s see the Lewis structure of IF3. As you already know, valence electrons are used to draw the Lewis structures of any molecule.
The Lewis structure of IF3 shows that I is surrounded by 2 lone pairs of electrons and forms 3 single bonds with each of the F atoms.
Let us check out the steps one should follow for drawing the Lewis structure:-
Step 1. The first and foremost step is to count the total number of valence electrons of the molecule.
Step 2. Next, we need to identify the central atom of the molecule.
Step 3. Now we start drawing chemical bonds between the central atom and the surrounding atoms. These bonds are represented by dots.
Step 4. Now we fill in the remaining valence electrons so that each atom has completed its octet which makes the overall molecule stable.
Step 5. If possible, convert lone pairs into double or triple bonds depending on the stability of the molecule.
As a last resort, we should always check the formal charge of each atom and make sure that it is the lowest possible.
The best Lewis structure for any molecule should have each atom with a formal charge of 0. The formal charge can be calculated by using the formula:-
Steps for Drawing Lewis Structure of IF3
Step 1. Let us start by counting the total number of valence electrons for the molecule IF3.
I and F both belong to group 7 and hence have 7 valence electrons each. But there are 3 atoms of F, so it will have 7×3= 21 valence electrons. Hence the total valence electrons for the molecule IF3 counts to 21+7= 28.
Step 2. The atom having the highest valence and the higher number of bonding sites is considered the central atom. So by definition, the central atom in IF3 is I.
Step 3. Now we start arranging the electrons as a chemical bond which is represented by two dots. Since there are three atoms of F, 6 valence electrons are used up.
Step 4. Now we arrange the valence electrons around each atom so that it completes its octet.
After completing the above procedure, we see that 24 valence electrons are used up. We still have 4 valence electrons remaining. So, these valence electrons will act as lone pairs on the central atom I.
Now I have more than 8 valence electrons. It can hold more than 8 valence electrons because atoms below period 5 can have an expanded octet and thus can carry more valence electrons. This is an exception to the octet rule.
Hence I have 2 lone pairs and can hold more than 8 valence electrons.
Step 5. Now that we have our Lewis structure, let us make sure that it is the best Lewis structure possible for IF3. If we check the formal charge of each atom for the molecule we see that each atom has a value of 0 which is the lowest possible.
Hence we do not need to convert the lone pairs into double/ triple bonds since we already have the best Lewis structure of the molecule IF3.
Thus, this Lewis structure of IF3 with 2 lone pairs is the most stable with each atom having a formal charge of 0.
Hybridization helps us to understand more about the nature of bonding in a molecule and is useful in determining the best, stable molecular shape of a molecule.
As the name suggests, molecules form a combination of hybrid orbitals to achieve more stability. The Hybridization of IF3 is Sp3d.
Hybridization of any molecule can found using the given methods:-
Method 1: The Addition Method:-
Hybridization of any molecule can be found by adding the total number of bonds formed by the central atom and the number of lone pairs on the central atom.
The value of Hybridization (H) is determined by:-
If H=2 denotes sp hybridization, H=3 denotes sp2 hybridization, H=4 denotes sp3 hybridization, H=5 denotes sp3d hybridization, and H=6 means sp3d2 hybridization.
We know that the Iodine atom is the central atom in IF3. It is bonded to 3 atoms of F and also has 2 lone pairs on it.
So when we add the number of bonded sites and lone pairs we get the value of H as 2+3 = 5, which means that IF3 is Sp3d hybridized.
Method 2: The formula method:-
The formula to find the Hybridization of any molecule is given below:-
Here, H represents hybridization on the central atom, V as valence electrons on the central atom of the molecule, M as the monovalent atoms bonded to the central atom, Cas charge on cation or more electropositive atom, and A represents the charge on anion or more electropositive atom.
The central atom of IF3 is I. So, V =7 (valence electrons of I). F is a monovalent atom and there are three F atoms bonded to I so M = 3.
Since the general charge of the molecule is neutral, both C and A are going to be zero.
Hence using the formula we get,
H=5 which clearly means that IF3 is Sp3d hybridized.
Thus, these two methods can be used to determine the Hybridization of any molecule.
IF3 Molecular Geometry
The molecular shape of any compound is formed due to the repulsion between the lone pairs and the bond pairs. Before we move further, let me clarify the difference between molecular shape and molecular/electron geometry.
The molecular shape does not take into account the lone pairs while molecular geometry does take lone pairs when determining the geometry. The electron geometry of IF3 is trigonal bipyramidal.
But the molecular shape of IF3 is T-shaped. The bond angles formed between each atom are close to 90 degrees.
The notation AXE is used to determine the molecular shape.
A= number of central atoms.
X = Atoms that are bonded to the central atom.
E= number of lone pairs on the central atom (non-bonding).
Let us now determine the molecular shape of IF3 using the above notation.
A=1 (I (Iodine) is the central atom).
X= 3 (3 F atoms).
E= 2 (2 lone pairs).
Putting in the values for each notation we get the formula as AX3E2 for IF3.
If we check this notation in the VSEPR chart given below we see that IF3 forms a T-shaped molecule.
ClF3 is also a similar molecule having its structure as well as hybridization same as IF3. Check out the article ClF3 Lewis Structure, hybridization, and Geometry.
IF3 is a polar molecule.
Now that we have learned how to draw the Lewis structure and the molecular shape of IF3, determining the polarity of the molecule will be a cakewalk.
If we look at the Lewis structure or the molecular shape of IF3, we see that it’s a T-shaped molecule. Now the electronegativity difference between I (2.5) and F (4.0) is greater than 0.5 thus inducing polarity.
From the structure of IF3, it is clear that the dipole moments do not cancel each other out as it does not have a symmetrical shape. All of these factors combine together to make IF3 a polar molecule.
In this article, we discussed important topics like the Lewis structure, hybridization, molecular shape, and polarity of IF3. Now you should be able to ace any questions about IF3 that come your way. If you have any doubts regarding any of the topics discussed above please feel free to address me.