Molecular Geometry, Hybridization, and Polarity of KCl Lewis Structure

The ionic salt potassium chloride (KCl) is made up of a metal (potassium) and a non-metal halogen (chlorine). As a result, it’s a metal halide with white or colourless cubic crystals. It has no odour and is very easy to dissolve in water.

The density of KCl is 1.984 g/cc, and its molar mass is 74.55 g/mol. It has a melting point of 7700 degrees Celsius and a boiling point of 14200 degrees Celsius.

A redox reaction occurs between KCl and Na, resulting in metal potassium, which is produced through distillation.

Na     +      KCL      <===>      NaCl     +     K   (850 degrees Celcius)

Potassium chloride is used in a variety of ways in our daily lives. It has therapeutic relevance since it is used to treat low blood pressure.

Potassium Chloride and Potassium Sulphate are two potash fertilisers that are made from it.

Apart from that, it’s utilised in soap production, food processing, anti-freezing chemicals, welding, soldering, and as a beta radiation source for calibration.

There are certain safety concerns and negative effects with KCl.

As a result, when handling or dealing with this chemical compound, suitable precautions should be used.

Lewis Structure of KCl

We need to know about the constituent atoms and the type of bond formation to comprehend the nature of chemical bonding inside any molecule.

We can see a clear picture of a 2D molecular composition, including electron dots and bond formation, by drawing a possible Lewis Structure.

Despite its limitations, Lewis Structure is the first step in interpreting chemical bonds.

We have a KCl molecule here, which is made up of one potassium atom and one chlorine atom.

The electrons in the element’s outermost shell that determine an atom’s valency are referred to as valence electrons. With the use of an element’s atomic number value, we may compute its valence electron number from the periodic table.

Let’s start by counting the valence electrons in the molecule.

This is a picture of the modern periodic table.

According to the periodic table, potassium belongs to group 1 and contains one valence electron. Chlorine, on the other hand, belongs to the halogen group 17 and has a valency of 7.

As a result, KCl has a total of 1 + 7 = 8 valence electrons.

Before we sketch the atomic elements and the electrons that surround them, it’s important to remember that KCl is an ionic compound, which means the two atoms are joined by an ionic connection rather than a covalent bond.

We discovered that two valence electrons are shared to form one bond in the event of covalent bond formation, as in NO. In ionic bonds, electrons are transported in order to create the bond.

We can see the atomic symbols for the constituent elements of a potassium chloride molecule in this diagram.

The valence electrons have been appropriately bonded here. The octet rule is now in effect.

The octet rule states that the elements in groups 1 to 17, i.e. the main group elements, have a tendency to fill their outer shell configuration, similar to noble gases. Carbon, for example, has an octet configuration to have the Neon configuration, while Silicon has the Argon configuration.

So, looking at our sketch, we can see that the Chlorine atom is one valence electron short of completing the octet, but K only possesses one.

Potassium will lose an electron and transfer it to chlorine in order for both elements to have eight valence electrons.

K’s electronic configuration has changed from 1s2 2s2 2p6 3s2 3p6 4s1 to 1s2 2s2 2p6 3s2 3p6 or [Ar].

And Cl’s, which was 1s2 2s2 2p5, is now 1s2 2s2 2p6 or [Ne].

As a result, they’ve both met the octet rule.

K now has a +1 positive charge as a result of losing an electron, while Cl now has a -1 negative charge as a result of receiving an electron.

We’ve found the molecule’s most suited Lewis Structure: potassium chloride.

We don’t mention the charges any longer while writing the compound:

K+    +     Cl-     ——->     KCl

We’ll now go on to the following segment.

Molecular Geometry of KCl

When we talk about covalent compounds, we use the VSEPR theory to deduce the molecular geometry from the Lewis Structure, which deals with lone pairs and bond pairs of electrons.

Electrons are not shared but transferred in ionic compounds, resulting in one atom carrying positive charges and the other bearing negative charges.

The crystal structure of the chemical will be discussed here in order to describe the 3D shape.

Ionic compounds with metals and non-metals in a 1:1 ratio are usually classified as FCC packing.

As a result, KCl has the same FCC arrangement as NaCl or sodium chloride, i.e., a Face Centered Cubic solid.

A unit cell will have four atoms in it, and the atoms will be tightly packed, occupying 74% of the entire volume.

The CCP (Cubic Close Packed) crystal is made up of chlorine anions. Potassium cations occupy the octahedral holes. Along the margins of the crystal-packed structure, both sorts of ions can now touch each other.

Hybridization with KCl

Orbital hybridization is a model that describes the fusion or mixing of atomic orbitals of the same atom with equal energies inside a molecule to produce hybridised orbitals. One s and three p orbitals, for example, combine to generate four sp3 hybrid orbitals.

This model is used to provide a logical explanation for bonding within covalent molecules.

We don’t need to hybridise KCl because we know K carries a +1 charge and Cl carries a -1 charge via charge transfer.

Polarity of KCl

A chemical compound’s polarity is another trait or quality. It is concerned with the separation of electric charges between atoms inside a molecular structure.

We must first comprehend the idea of electronegativity in order to determine whether a chemical is polar or nonpolar in nature.

Electronegativity is a property of an element that governs or denotes the amount of electrons (negative charges) that it can gain.

If there are components in a molecule with varying electronegativity values and the difference is significant, charge separation occurs.

A polar bond is formed when the more electropositive atomic element has a partial positive charge and the other has a partial negative charge.

Now we must figure out how to determine the electronegativity of K and Cl.

The Pauling electronegativity chart is shown below:

K has a value of 0.82 and Cl has a value of 3.16, as seen in the table.

The difference is estimated to be roughly 2.34.

When the electronegativity difference is less than 0.4, a molecule is now called non-polar or pure covalent. Polar covalent is defined as a number that varies from 0.4 or 0.5 to roughly 1.8-2.

The fact that the result is 2.34 indicates that the binding is ionic.

The nature of the bond gets more ionic as the electronegativity difference increases. In polar liquids, KCl, or potassium chloride salt, dissolves and dissociates into K+ and Cl- ions.


We’ve gone through the bonding nature of the KCl (potassium chloride) molecule in great detail in this post.

Good luck with your studies!

Read more: Molecular Geometry, Hybridization, and Polarity of CH2N2 Lewis Structure

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


Please enter your comment!
Please enter your name here

Read More