Is HCl an Ionic or a Covalent Compound?

Hydrochloric acid (HCl) is also known as muriatic acid. It is a member of the hydrogen halide family (HX). Hydrogen halides are inorganic diatomic compounds that, due to their tendency to lose proton in solution, act as Arrhenius acids. The X can be fluorine, chlorine, bromine, or iodine because it belongs to the halogen family (group 17).

A colourless and transparent solution of hydrogen chloride in water is known as hydrochloric acid. It’s a powerful acid with a strong odour.

The melting and boiling temperatures of hydrogen chloride solution are not constant because they are affected by the concentration of the aqueous solution. The pH and density of the hydrogen chloride solution are also not set in stone.

We can see fumes in the air with a distinct scent if we open a bottle of concentrated HCl solution.

Our stomachs contain hydrochloric acid, which aids in food digestion. Acidity concerns are caused by a high concentration of this acid in the stomach.

HCl is employed in the synthesis of a variety of organic and inorganic chemicals, as well as the regeneration of ion exchanges used in water purification.

So, is HCl an ionic or a covalent compound? Because the electronegativity difference between hydrogen and chloride is smaller than 2.0, HCl is a covalent molecule. However, because chlorine is more electronegative than hydrogen, it will draw a shared pair of electrons towards itself, making it a genuine covalent molecule. As a result, the HCl molecule has a 17 percent ionic character and is a covalent compound.

The H-Cl bond will behave as a dipole in the HCl molecule, with a partial positive charge on the hydrogen atom and a partial negative charge on the chlorine atom, respectively.

Partially charged HCl has a partial charge of 0. 027 x 1018 C.

Let’s take a closer look at the covalent nature of hydrogen chloride.

To do so, we must first understand the fundamentals of chemical bonding, such as what a chemical bond is and how it is produced.

Chemical Relationship

First, let’s take a look at a contemporary periodic table.

Except for group 18 members, atoms from the contemporary periodic table do not exist freely in nature, as we all know. As a result, they mix with either the same atom or a different atom to generate elements and compounds, respectively.

A chemical bond is a force of attraction between two same or dissimilar atoms that aids in bringing them together.

What causes chemical bonding to form?

Protons, electrons, and neutrons are the subatomic particles that make up an atom. Only electrons participate in the development of a link among these three particles.

We know that an atom’s atomic number equals the number of electrons in the atom.

Now, the question arises as to whether all of an atom’s electrons participate in bond formation.

No, not all electrons are involved in the bonding process. The only electrons present in the atom’s outermost shell contribute to bond formation. Valence electrons are the name for these electrons.

The electrons in the inner shell of the atom are known as Core Electrons, and they do not participate in the bond forming process.

As a result, when two atoms share their electron density, a chemical connection is established. The distribution of electron density between atoms might be equal or uneven.

Chemical Bonds: What Are They and How Do They Work?

Ionic and covalent chemical bonds are the two types of chemical bonds found in molecules.

Ionic Bonds: Ionic bonds are created when electrons are transferred from one atom to another. In an ionic bond, cations and anions are attracted by an electric force.

Covalent Bonds: Covalent bonds are created when two atoms share an electron pair (s). Depending on the number of electron pairs shared by two atoms, covalent bonds are classed as single, double, or triple bonds.

Now, how can you tell whether a chemical link is ionic or covalent?

Obviously, looking at the atoms involved in bond formation will not provide an answer to this question. To distinguish between ionic and covalent bonding, we need a quantitative parameter. Electronegativity values are the parameter in question.

What is electronegativity, please?

Electronegativity

It is an atom’s property that causes it to draw the shared electron pair towards it. The Pauling scale is used to calculate the electronegativity of the atoms.

Ionic bonds are defined as chemical bonds in which the electronegativity difference between two atoms in a chemical bond is greater than 2.0. If the difference is less than 2.0 on the Pauling scale, a covalent bond is present.

Why does HCl have a covalent bond in nature?

When it comes to hydrogen chloride (HCl),

The hydrogen atom has an electronegativity of 2.20.

The chlorine atom has an electronegativity of 3.16.

The H-Cl bond has an electronegativity difference of 0.96.

On the Pauling scale, the electronegativity difference of the H-Cl bond is just 0.96, indicating that the H-Cl link is covalent.

As a result, hydrogen chloride is classified as a covalent compound.

Hydrogen chloride, on the other hand, is not a real covalent compound. What are real covalent compounds, and why are they so?

What makes HCl a non-covalent compound?

In homonuclear compounds, such as H-H, F-F, and Cl-Cl, for example, a genuine covalent bond is created when each atom in the molecule shares an equal amount of electrons.

When there are heteronuclear molecules, however, the covalent character, or purity of covalency, declines. H-Cl, H-Br, and H-I, for example. Because of the disparity in electronegativity values, atoms in heteronuclear compounds do not share electrons equally.

As a result, HCl is not a real covalent molecule since the chlorine atom, due to its stronger electronegativity (3.16) than the hydrogen atom, will draw a shared pair of electrons towards itself (2.20).

The H-Cl link in the hydrogen chloride molecule is also known as a polar covalent bond. It means that the H-Cl bond is a dipole, with the hydrogen atom having a partial positive charge and the chlorine atom having a partial negative charge.

It would be fascinating if we could compute the atom’s partial charge. So, in hydrogen chloride, let’s compute the partial charge on the hydrogen and chlorine atoms.

In a polar covalent bond, the charge is defined as the ratio of the molecule’s dipole moment () to the distance between the two atoms (d). The following is the charge measurement formula:

Q = μ/d

The charge is measured in D/m or C since the dipole moment is measured in D (Debye) and the distance is measured in m. (Coulomb).

The hydrogen chloride dipole moment is 1.05 D, while the distance between the hydrogen and chlorine atoms in the compound is 127.4 * 10-12 m.

1 D = 3.33 × 10−30 C. m

The partial charge on the hydrogen atom is 0.027 x 10-18 C when the values in the previous equation are substituted.

On the chlorine atom, there will be an equal but opposite charge, i.e., –0.027 x 10-18 C. As a result, the partial charge value in the hydrogen chloride compound is 0. 027 x 1018 C.

Next, we’ll calculate the percentage of electrons transported from the hydrogen atom to the chlorine atom in hydrogen chloride, which has a well-known Ionic property in the covalent bond.

One electron has a charge of 1. 6022 1019 C, as we know.

(Partial charge on the atom 100) / Charge on one electron Equals Percentage of Ionic Character

= (0. 027 x 10−18 ∗ 100)/1. 6022 × 10−19 C

= 17 %

As a result, just 17 percent of the electron density from the hydrogen atom to the chlorine atom in hydrogen chloride has been transported.

It proves that the hydrogen chloride’s H-Cl bond is a polar covalent bond rather than an ionic bond. Another way to distinguish between ionic and covalent bonding is to use this criterion.

As a result, the hydrogen chloride molecule is a 17 percent ionic covalent complex.

Conclusion

We looked at the covalent nature of the hydrogen chloride compound in this article.

In a nutshell, hydrogen chloride is a covalent compound formed by the difference in electronegativity of two atoms in the HCl molecule. This covalent molecule does, however, have some ionic character, which is estimated to be 17 percent. It validates the polar covalent character of the H-Cl link in the HCl molecule.

Finally, the hydrogen chloride molecule is a polar covalent compound with a partial charge of 0.027 x 1018 C and a 17 percent ionic character.

Read more: Does HBr Polar or Nonpolar?

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.

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