I3 Lewis Structure

Let’s know about the I3 Lewis Structure. I3 Lewis structure I3 or triiodide ion is a polyatomic or charged molecule with a net negative charge of -1.

I2 + I-—-> I3-

It is this external equilibrium that leads to the formation of ions where there is a positive flow of energy from the system to the environment. One of the main uses of this ion is due to its non-reactive property with starch resulting in the widely used blue-black colorant for identification.

What is Lewis Structure I3?

I3 Lewis Structure

The Lewis structure is a reflection of molecular electrons. Lone pairs and valence electrons are what help determine the hybridization and form of the molecule. Since there are iodine molecules, there will be one iodine molecule in the center . Iodine is also in the seventh group of the periodic table and has seven valence electrons in its outermost shell .

We have three iodine molecules here, plus an extra electron that gives it a negative charge. So the total number of valence electrons is: 7 * 3 + 1 = 22.

The total number of valence electrons in this molecule is 22. Now there is an octet rule which an atom obeys. According to this law there should be eight electrons per atom in its outermost orbit?

If the central atom has 8 electrons in its outermost shell, there are two other atoms that need to complete their octet. Since all atoms need eight electrons in their outermost orbital to complete the octet, both neighboring iodine atoms will take one electron from the central iodine atom. He would say 8-1-1=6.

Since electrons are taken from both the atoms.

So now there will be six valence electrons on the central iodine atom. Lone pairs of electrons that are not bonded will form these six electrons. There will be three lone pairs of electrons and two bond pairs because each iodine atom has one bond with the central atom, which has one electron each, with a total of 3 lone pairs and 2 bond pairs on the central atom as it is now carrying electrons . Makes a pair. ,

Hybridization of I3.

To learn about I3 Lewis structure we will now learn about hybridization of I3. There is a basic formula that can be used to understand the hybridization of any molecule. This formula is used to find out the number of hybridizations which help in understanding the hybridization of the molecule.

The number of hybrids and hybridizations defined by it are as follows:

  • hybridization in sp.
  • Hybridization SP2
  • Hybridization SP3
  • hybridization

The formula to find the number is,

Number of Hybridization: Valency Electron Number + Monovalent + (Negative Charge)-(Positive Charge)/2

Iodine atoms have 7 valence electrons because there are seven electrons in the outermost shell. Since two of the three iodines are monovalent, the monovalent atomic number is two.

When we get to the charge of the I3-ion it now has a negative charge, so the amount of this negative charge will be 1.

Now, position all the values, according to the formula

7 + 1 + 2/2 2/2

=10/2/2 =5

Therefore, the hybridization number is 5, which means that there is sp3d hybridization.

There is another way to find the hybridization of a given molecule, using lone pairs and valence electrons. The number of lone pairs in this molecule is 3 and the number of valence electrons shared by the atoms is 2.

Thus, 3+2=5, which also specifies the hybridization of sp3d?

Size of i3

The molecule shape is linear in the I3-form. Iodine has three atoms, one of which has an additional negative charge. This one extra electron has 3 lone pairs of electrons and 2 bond pairs, making it the steric number 5. These pairs try to repel each other as much as possible because there are three lone pairs on the central iodide atom.

So the pairs take the equatorial position at greater distances, and the other two iodine atoms are 180 degrees away from each other. Thus the overall form of the I3-ion is 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 molecules we see are charged ions. Since I3- has one electron, this ion has an overall negative charge. Molecules have polarity because they all have charges that are partly positively charged and partly negatively charged.

Molecules have dipole moment based on the separation of charges on the atom. If the distance between the two charges is greater then the dipole moment will also be large.

But I3-ion is a negatively charged ion when we talk about it. We do not see any dipole moment of polar bonds in it because the total charge on the ion is negative even though we draw its Lewis structure. So it is not polar or non-polar either. Still, if you have to define an ion, you can use the term like a polar molecule because I3- is soluble in water.

Properties of Tri-iodide Ion

Let us discuss those features of the triiodide molecule.

The triiodide anion, from which most polyiodes exist, is the simplest polyiodide. It appears yellow in low concentration and brown in solution at high concentration. The blue-black color is attributed to the triiodide ion, a well-known one that occurs when an iodine solution interacts with starch, or when a non-polar solution does not contain an iodine solution.
Lugol’s iodine contains elemental iodine and a stoichiometric amount of potassium iodide, so this solution contains a large amount of the 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 iodine has three atoms, one of the atoms has a negative charge that also provides two pairs of bonds and three lone pairs of electrons. Stereo would be number five. 3 lone pairs are driven out and equatorial positions are taken. The remaining two atoms of iodine are 180 degrees away from each other.


As well as the structures of many molecules and multiatomic ions with a central metal atom, the VSEPR model can predict the structure of almost any molecule or multiatomic ion in which the central atom is a nonmetal. The model of VSEPR is not a theory; It doesn’t try to explain the comments.

Instead, it is a counting process that effectively reformulates the three-dimensional structures of a large number of compounds, which could not be predicted using the Lewis electron-pair approach.

VSEPR model of tri-iodide ion

  1. Seven electrons and one negative charge are added by each iodine atom, so the Lewis electron structure is linear.
  2. In I3, there are five electron groups, two bond pairs and three lone pairs around the central atom. The groups are drawn at the corners of a triangular bipyramid to minimize repulsion.
  3. I3′ has a total of five electron pairs with two bond pairs and three lone pairs. Now we have to determine how to arrange the lone pairs of electrons in a triangular dipyramid in such a way that the repulsion is minimized. This removes the 90° LP-LP repulsion by keeping it in axial position and reduces the number of 90° LP-BP repulsion.
  4. There are equivalent interactions of three lone pairs of electrons with the three iodine atoms, so we see no change in the bonding angles.
  5. The molecular geometry of I3− is linear with three nuclei and three lone pairs of electrons. It can be described as a triangular bipyramid with three missing equatorial vertices. As predicted, the ion has a III angle of 180°.

lone pair of I3.

An iodine atom has three lone pairs of electrons. I3(-) has 3 lone electron pairs in the central atom and forms two bonds with adjacent iodine. Hence, it 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 the ion triiodide. It is a polyhalogen anion and is composed of three atoms of iodine. It is formed by mixing iodide salts and iodine in an aqueous solution. It is a linear atom and is formed by binding of I2 and I(-) ions. Triiodide is red in solution. I(-) is a donor atom in this molecule and I2 is an acceptor atom.

The electrons are accommodated in the vacant d orbital of iodine. During the combination of iodine atoms the central atom acquires a negative charge whose value is 1. The tri iodide ion hybridization is SP3D. With a bond angle of 180°, the geometry of the tri-iodide anion is linear.

Frequently Asked Questions For I3 Lewis Structure

Below you find some of the most common questions about the Lewis structure of I3 which may also help chemistry students.

Does the i3 have a whole lot of one octave?

The Lewis dot of the triiodide ion I3 does not obey the octet rule. It will hold more than 8 electrons. At the fourth energy level, iodine with valence electrons will also have access to the 4d sublevel, thus allowing more than 8 electrons.

Why is i3 linear?

I3 is the linear 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. Three lone pairs will repel each other and assume the equatorial position.

is i3 nonlinear or linear?

For the 5 regions of electron density, I3- has 2 bonds and 3 lone pairs. The lone pair goes equatorial and the other two I atoms go axial, placing it in a triangular bipyramidal structure. The molecule is linear, consisting of three atoms in a row.

Is I3 an extended octave?

The I3 ion does not obey the Lewis dot-octet rules of the I3 triiodide. It has more than 8 electrons. Iodine, which has valence electrons at energy level 4, can reach levels below 4, thus having more than 8 electrons.

Why is i3 but not f3?

The F3 ion is absent because it is small and there is no free d-orbital to expand the covariance from one to two when iodine is large, and the d-orbital is empty to form the I3 ion. No ions.

What is I3 negative hybridization?

Now it has negative charge on the charge of I3-ion. Therefore, the value of this negative charge is 1, hence the hybrid number is 5. This means that it is a sp3d hybrid. Another way to find inbreeding for a particular molecule is to use the lone pair and valence electrons.

Why is I3 soluble in water?

Potassium iodide reacts with iodine to form the triode ion as a precursor. Use the Le Chatelier principle (equilibrium to compensate for system changes) to explain why iodine dissolves in water. Increases with increasing concentration of potassium iodide.

Does I3 have a coordinate link?

Linearly, I-3 (triode ion) has a central iodine atom. We can say that the I-negative charge is reset to I-3 or transferred to the central iodine by the positive charge of the coordinate covalent bond.

Does bf3 have a full octave?

A molecule that lacks an electron… boron forms only three covalent bonds, leaving only six valence electrons around the B atom. A well-known example is Bf3: a third violation of the octet law is found. A compound with more than eight electrons is assigned to its valence shell.

Why is I3 more stable?

Only the lowest trajectory is connected. But since it is about the overlap of three atoms instead of two atoms, it is a stronger bond than the two-centre bond in I2.


In closing remarks, I3- is a polyatomic ion with 22 valence electrons, 3 lone pairs, 2 bond pairs, and sp3d hybridization, in short, that’s the whole article. In shape, it is linear and has no polarity.