Knowing the i3 Lewis structure and understanding its physical properties, hybridization, and molecule shape is critical. We are going to go through the Lewis structure of I3 today, or we also know it as a Tri-iodide ion because it has a negative charge on it. There are three iodine molecules in this molecule, which is why Tri-iodide is the name of the compound.
What is the Lewis Structure?
The structure of Lewis is a reflection of molecular electrons. There are lone pairs and valence electrons that assist in determining the molecule’s hybridization and form. Since there are iodine molecules, there will be one iodine molecule in the center. Iodine is also in the periodic table’s seventh group and has seven valence electrons in its outer orbit.
We have three iodine molecules here, along with an extra electron that gives a negative charge. So the total number of electrons of valence is: 7 * 3 + 1 = 22.
The total number of valence electrons is 22 in this molecule. Now there is an octet law that is followed by an atom. Per atom should have eight electrons in its outer orbit, as per this law?
If in the outer shell of the central atom there are 8 electrons, there are two other atoms that need to complete their octet. As all atoms need eight electrons in their outer shell to complete the octet, both the neighboring iodine atoms will take one electron from the central iodine atom. That would say 8-1-1=6.
Since the electrons are taken from both atoms.
So now there will be six of the valence electrons on the central iodine atom. The lone pairs of electrons which do not bind will form these six electrons. There will be three lone pairs and two bond pairs of electrons as each iodine atom has a bond with the central atom sharing one electron each with a total of 3 lone pairs and 2 bond pairs on the central atom as it forms the pair of electrons now.
Hybridization of I3
There is a basic formula that can be used for understanding the hybridization of any molecule. This formula is used to figure out the number of hybridizations that help to understand the molecule’s hybridization.
The numbers of the hybrid and the hybridization it defines are as follows:
Hybridization in sp
The number finding formula is,
Number of hybridization: Valence electron number + monovalent + (negative charge)-(positive charge)/2
The iodine atoms’ valence electrons are 7 since there are seven electrons in the outermost shell. Since two out of three iodines are monovalent, the monovalent atom number is two.
It has a negative charge now when we get to the charge of the I3-ion, so the amount of this negative charge would be 1.
Now, according to the formula, position all the values
7 + 1 + 2 /2 2/2
Therefore, the hybridization number is 5, which means that sp3d is hybridization.
Using lone pairs and valence electrons, another way to find the hybridization of a given molecule is. In this molecule, the number of lone pairs is 3, and the number of valence electrons sharing atoms is 2.
Thus, 3+2=5, which also specifies the hybridizations of sp3d?
The shape of I3-
The molecule shape I3- is linear in form. There are three atoms of iodine, of which one has an additional negative charge. There are 3 lone pairs of electrons and 2 bond pairs due to this one extra electron, which makes it steric number 5. These pairs attempt to repel each other as much as possible since there are three lone pairs on the central Iodide atom.
So the pairs take equatorial positions to be away at a greater distance, and the other two iodine atoms are 180 degrees from each other. The overall form of the I3-ion is thus linear.
Polarity of i3
So here’s the tricky thing about this ion, we should call it a polyatomic ion instead of calling it a molecule, first of all, like it as a charge on it. The charges on the molecules that we see are ions. Since I3- has one electron, this ion has an overall negative charge. Molecules have polarity because they all have charges that are partly charged positively and partly charged negatively.
Depending upon the separation of the charges on the atom, there is a dipole moment on the molecules. The dipole moment would also be larger if the distance between both charges is greater.
But the I3-ion is a negatively charged ion when we talk about it. We do not see any dipole moment of the polar bonds in it as the total charge itself is negative on the ion, even when we draw its Lewis structure. So it’s not polar or nonpolar either. Nevertheless, if you have to define the ion, you can use the term like a polar molecule because I3- is water-soluble.
Properties of Tri-Iodide Ion
Let us discuss those characteristics of the triiodide molecule.
- The triiodide ion, from which most polyiodides exist, is the simplest polyiodide. It appears yellow in the low concentration and brown in the solutions in the higher concentration. The blue-black color is responsible for the triiodide ion, a well-known one that happens when iodine solution interacts with starch, or when iodine solutions in the non-polar solution do not occur.
- Lugol’s iodine contains a stoichiometric quantity of elemental iodine and potassium iodide, so this solution contains a large amount of triiodide ion.
- Iodine tincture, which is a nominal solution of elemental iodine in ethanol, also contains a large amount of tri iodide due to its iodide and water content.
Molecular Geometry of I3
Linear is the molecular geometry of I3. While there are three atoms of iodine, one of the atoms has a negative charge that also provides two pairs of bonds and three lone pairs of electrons. The stereo number will be five. The 3 lone pairs are repelled and the equatorial positions are taken up. The remaining two atoms of iodine are 180 degrees apart from each other.
The VSEPR Model
As well as the structures of many molecules and polyatomic ions with a central metal atom, the VSEPR model can predict the structure of nearly any molecule or polyatomic ion in which the central atom is a nonmetal. The model of the VSEPR is not a theory; it does not try to explain observations.
Instead, it is a counting process that effectively improves a large number of compounds’ three-dimensional structures, which could not be predicted using the Lewis electron-pair approach.
VSEPR Model of Tri-iodide Ion
- Seven electrons and one negative charge are added by each iodine atom, so the Lewis electron structure is linear.
- In I3, there are five electron groups, two bonding pairs, and three lone pairs, around the central atom. The groups are drawn to the corners of a trigonal bipyramid to mitigate repulsion.
- I3’ has a total of five electron pairs with two bonding pairs and three lone pairs. We must now determine how in a trigonal bipyramid to organize the lone pairs of electrons in a way that minimizes repulsions. It removes 90° LP-LP repulsions by positioning them in the axial positions and minimizes the number of 90° LP-BP repulsions.
- There are equivalent interactions of the three lone pairs of electrons with the three iodine atoms, so we do not foresee any variations in bonding angles.
- The molecular geometry of I3− is linear with three nuclei and three lone pairs of electrons. This can be described as a trigonal bipyramid with three missing equatorial vertices. As predicted, the ion has an I-I-I angle of 180°.
Lone Pairs of I3
There are three lone pairs of electrons in an iodine atom. The central atom in I3(-) has 3 lone electron pairs and produces two bonds with adjacent iodine. It, therefore, carries a negative charge on it. Thus, the total number of lone electron pairs in the I3 structure is 9.
I3 is generally referred to as ion triiodide. It is a polyhalogen ion and is made up of three atoms of iodine. It is formed by mixing iodide salts and iodine in an aqueous solution. It is a linear atom and it is formed by I2 and I(-) ion binding. In solution, triiodide is red. I(-) is a donor atom in this molecule and I2 is an acceptor atom.
In the empty d orbital of iodine, the electrons are accommodated. The central atom gains a negative charge whose value is 1. during the combination of iodine atoms. Tri iodide ion hybridization is SP3D. With a bond angle of 180 degrees, the geometry of tri-iodide ions is linear.
Frequently Asked Question (FAQs)
Below you get some most common questions about the Lewis structure of I3 which can also helps the students of chemistry.
Does i3 have an octet in its entirety?
Lewis Dot of Triiodide Ion I3- The octet rule is not followed by me. More than 8 electrons will hold it. At the 4th energy level, iodine with valence electrons will also have access to the 4d sublevel, thus allowing for more than 8 electrons.
Why is i3 linear?
I3- linear is molecular geometry. While there are three iodine atoms, one of the atoms has a negative charge, providing 3 lone electron pairs and 2 bond pairs. The three lone pairs will repel one another and take equatorial positions.
Is i3 nonlinear or linear?
For 5 regions of electron density, I3- has 2 bonds and 3 lone pairs. The lone pairs go equatorial and the other two I atoms go axial, placing this into a trigonal bipyramidal structure. The molecule is linear, with three atoms in a line.
In closing remarks, I3- is a polyatomic ion that has 22 valence electrons, 3 lone pairs, 2 bond pairs, and sp3d hybridization, to sum up, this entire article. In shape, it is linear and has no polarity.