Carbon tetraiodide (CI4) lewis dot structure, molecular geometry, polar or nonpolar, hybridization

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CI4 lewis structure molecular geometry

Carbon tetraiodide appears as dark violet crystals with the chemical formula CI4. It can react with water to form iodoform and I2. 

In this tutorial, we will discuss CI4 lewis structure, molecular geometry, polar or nonpolar, etc.

Carbon tetraiodide is irritant and has a density of 4.32 g mL−1. The carbon weight in CI4 is just 2%. 

Name of MoleculeCarbon tetraiodide
Chemical formulaCI4
Molecular geometry of CI4Tetrahedral
Electron geometry of CI4Tetrahedral
HybridizationSp3
NatureNonpolar
Total Valence electron for CI432

How to draw lewis structure of CI4?

CI4 lewis structure contains carbon atom at middle position whereas four iodine atoms surround to it. A total of 12 lone pairs and 4 bonded pairs are present in the lewis structure of CI4.

The lewis structure of CI4 is similar to CCl4 and CF4, since, they all are in the same group in the periodic table and contain the same number of valence electrons.

Follow some steps for drawing the Lewis dot structure for CI4

1. Count total valence electron in CI4

First of all, determine the valence electron that is available for drawing the lewis structure of CI4 because the lewis diagram is all about the representation of valence electrons on atoms.

So, an easy way to find the valence electron of atoms in the CI4 molecule is, just to look at the periodic group of carbon and iodine atoms.

As the carbon atom belongs to the 14th group in the periodic table and iodine is situated in the 17th group, hence, the valence electron for the carbon is 4, and for the iodine atom, it is 7.

⇒ Total number of the valence electrons in carbon = 4

⇒ Total number of the valence electrons in iodine = 7

∴ Total number of valence electrons available for the CI4 Lewis structure = 4 + 7×4 = 32 valence electrons         [∴CI4 molecule has one carbon and four iodine atoms]

Total number of valence electron available for the CI4 Lewis structure

2. Find the least electronegative atom and place it at center

As we know, electronegativity increase as we move from left to right in the periodic table. Hence, the iodine atom is more electronegative than a carbon atom. Therefore, it can never be placed in a central position because it is less prone to share electrons.

So, place the carbon in the middle position and spread the four iodine atoms around it.

central atom in CI4 lewis structure

3. Connect outer atoms to central atom with a single bond

In this step, join all outer atoms to the central atom with the help of a single bond.

In, CI4 molecule, iodine is the outer atom, and carbon is the central atom. Hence, joined them. 

skeletal structure of CI4

Now look at the above structure and count the number of valence electrons we used till now. A single bond means 2 valence electrons. In the above structure, four single bonds are used for connecting each iodine atom to a carbon central atom.

Hence, (4 × 2) = 8 valence electrons are used from a total of 32 valence electrons that are available for drawing the lewis structure of CI4.

∴ (32 – 8) = 24 valence electrons

So, we are left with 24 valence electrons more.

4. Place remaining electrons on the outer atom first and complete their octet

In this step, we have to put the remaining valence electron over each outer atom to complete their octet first. We know, in the CI4 molecule, iodine is the outer atom, hence, each iodine atom needs 8 electrons in its outer shell to complete the octet and attain stability.

So, just start putting out the remaining valence electron around each iodine atom until they complete their octet.

CI4 lewis structure

So, by looking at the above structure, we see each iodine atom gets 6 valence electrons represented as dots, and they also have 2 valence electrons in form of a single bond that is attached to them.

Hence, (6 valence electrons as dots + one single bond that contains 2 electrons) = 8 valence electrons are present around each iodine atom, hence, they all completed their octet.

Also, the central atom Carbon also completed its octet as it has four single bonds attached that means, it has 8 valence electrons in its valence shell.

Now check the formal charge for the above CI4 lewis structure.

5. Check the stability with the help of a formal charge concept

“The lesser the formal charge on atoms, the better is the stability of the lewis diagram.”

To calculate the formal charge on an atom. Use the formula given below-

⇒ Formal charge = (valence electrons – lone pair electrons –  1/2 bonded pair electrons)

Let’s start with the central atom which is carbon in the CI4 molecule.

For carbon atom:

⇒ Valence electrons of carbon = 4

⇒ Lone pair electrons on carbon = 0

⇒ Shared pair electrons around carbon(4 single bond) = 8

∴ (4 – 0 – 8/2) = 0 formal charge on the carbon central atom.

Each iodine atom in the CI4 lewis structure has the same number of lone pair and bonded pair electrons, hence, just count formal charge for just one iodine atom

 For iodine atom

⇒ Valence electrons of iodine = 7

⇒ Lone pair electrons on iodine = 6

⇒ Shared pair electrons around iodine (1 single bond) = 2

∴ (7 – 6 – 2/2) = o formal charge on each iodine atom.

formal charge in CI4 lewis structure

CI4 lewis structure

So, each atom gets the formal charge equal to zero, hence, the above lewis structure of CI4 is most stable and reliable.

What is the molecular geometry of CI4?

The molecular geometry of CI4 is tetrahedral because the central atom carbon is bonded with four iodine atoms and it contains no lone pair that means, it is an AX4 type molecule.

A represent central atom

X represent the number of bonded atom to central atom

According to VSEPR theory or chart, the AX4 type molecule forms tetrahedral molecular geometry or shape.

Hybridization of CI4

The hybridization of CI4 is Sp3 because the steric number of the carbon central atoms is four.

The calculation of steric number is done by adding a number of bonded atoms attached to the central atom and lone pair on the central atom.

In the case of the CI4 molecule, carbon is the central atom that is attached to the four bonded atoms(iodine) and it has no lone pairs.

Hence, (4 + 0) = 4 is the steric number of central atom carbon in the CI4 molecule that gives Sp3 hybridization.

Is CI4 polar or nonpolar?

So, Is CI4 polar or nonpolar? CI4 has a tetrahedral molecular shape that is highly symmetrical, so all the dipoles of the 4 polar C-I bonds cancel each other out, resulting in an overall nonpolar molecule. Although the bond C-I is polar in nature because of the difference of electronegativity between them but the overall CI4 molecular is nonpolar.

Properties of Carbon tetraiodide

  • It has magnetic susceptibility of -136·10−6 cm3/mol.
  • It is soluble in nonpolar organic solvents.
  • It has a molar mass of 519.629 g·mol−1.
  • It is thermally and photochemically unstable.
  • It is irritant and somewhat toxic in nature.

Summary

  • The total valence electron is available for drawing the CI4 Lewis structure is 32.
  • The molecular geometry or shape of CI4 is tetrahedral.
  • CI4 is nonpolar and has Sp3 hybridization.
  • In the CI4 Lewis structure, a total of 24 nonbonding electrons and 8 bonded electrons are present.
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