Difference Between Homonuclear and Heteronuclear Diatomic Molecules

Key Difference – Homonuclear vs Heteronuclear Diatomic Molecules
 

Diatomic molecules are substances composed of two atoms per molecule. These molecules are composed of two atoms bonded to each other via covalent chemical bonds. The atoms can be bonded via single bonds, double bonds or triple bonds. Depending on the types of atoms present in the diatomic molecule, there are two types of diatomic molecules: homonuclear diatomic molecules and heteronuclear diatomic molecules. The key difference between homonuclear and heteronuclear diatomic molecules is that homonuclear diatomic molecules contain two atoms of the same element whereas heteronuclear diatomic molecules contain two atoms of different elements.

CONTENTS

1. Overview and Key Difference
2. What are Homonuclear Diatomic Molecules
3. What are Heteronuclear Diatomic Molecules
4. Similarities Between Homonuclear and Heteronuclear Diatomic Molecules
5. Side by Side Comparison – Homonuclear vs Heteronuclear Diatomic Molecules in Tabular Form
6. Summary

What are Homonuclear Diatomic Molecules?

Homonuclear diatomic molecules are substances composed of two atoms of the same chemical element bonded to each other via a covalent bond(s). Therefore, the atoms of a homonuclear diatomic molecule are the same. A homonuclear diatomic molecule is also known as a mononuclear compound. The chemical elements that form homonuclear diatomic molecules often are hydrogen, nitrogen, oxygen, and halogens. Noble gases do not form diatomic molecules.

Figure 1: A Model of a Homonuclear Diatomic Molecule

The two atoms of the homonuclear molecule are same; thus the electronegativity is also equal. Then the bond electron pairs between the two atoms are equally distributed, and the chemical bond between the two atoms is nonpolar. There can be single bonds, double bonds or triple bonds between the atoms of the homonuclear diatomic molecule.

Examples

• Hydrogen molecule (H₂) contain a single bond between two hydrogen atoms.
• Oxygen molecule (O₂) contains a double bond between two oxygen atoms.
• Nitrogen molecule (N₂) contains a triple bond between two nitrogen atoms

What is Heteronuclear Diatomic Molecules?

Heteronuclear diatomic molecules are substances composed of two atoms of two different chemical elements bonded to each other via a covalent bond(s). Therefore, the atoms of the heteronuclear diatomic molecule are different from each other.

Figure 2: A Model of a Heteronuclear Diatomic Molecule

The electronegativity of the two atoms of the heteronuclear diatomic molecule is different from each other because they belong to different chemical elements (different chemical elements have different electronegativity values). Then the chemical bonds between these atoms are polar bonds. This is because the bond electrons are attracted by the electronegative atom (the atom that is more electronegative compared to the other atom).

Examples

• Hydrogen fluoride (HF) has a single bond between the hydrogen atoms and the fluorine
• Nitrogen oxide (NO) has a double bond between the nitrogen atom and the oxygen atom (and there is an unpaired electron on nitrogen atom).
• Carbon monoxide (CO) has a triple bond between carbon and oxygen atoms.

What are the Similarities Between Homonuclear and Heteronuclear Diatomic Molecules?

• Both types of molecules have only two atoms per molecule.
• Both types of molecules have a linear geometry.
• Both types of molecules contain covalent chemical bonds.

What is the Difference Between Homonuclear and Heteronuclear Diatomic Molecules?

Summary – Homonuclear vs Heteronuclear Diatomic Molecules

Homonuclear diatomic molecules are composed of identical atoms of the same chemical element, but heteronuclear diatomic molecules have atoms of two different chemical elements. The key difference between homonuclear and heteronuclear diatomic molecules is that homonuclear diatomic molecules contain two atoms of the same element whereas heteronuclear diatomic molecules contain two atoms of different elements.

Reference:

1. Helmenstine, Anne Marie. “What to Know About Diatomic Molecules.” ThoughtCo, Available here.
2. “Homonuclear molecule.” Wikipedia, Wikimedia Foundation, 28 Feb. 2018, Available here.
3. Mott, Vallerie. “Introduction to Chemistry.” Lumen, Available here.

Image Courtesy:

1. “Chlorine-3D-vdW” (Public Domain) via Commons Wikimedia
2. “Chlorine-monofluoride-3D-balls” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia

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