Polar and Nonpolar Covalent Bond

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Polar and Nonpolar Covalent Bond

This lesson aligns with NGSS PS1.A

Introduction

A covalent bond is characterized by the sharing of electrons between atoms, contributing to the stability and integrity of molecules. Unlike other types of bonds, such as ionic bonds where electrons are transferred, covalent bonds involve a cooperative sharing mechanism. This shared electron arrangement creates a strong connection between the participating atoms, influencing the physical and chemical characteristics of the resulting compounds. In this article, we will learn about polar covalent bond, properties of polar covalent bond, nonpolar covalent bond and properties of nonpolar covalent bond.

Polar Covalent Bond

A covalent bond tends to be polar when the sharing of electrons is unequal between the participating atoms. This asymmetry in electron sharing is a consequence of the variance in electronegativities exhibited by the two atoms involved in the bond.

Electronegativity quantifies an atom's tendency to attract a shared pair of electrons, and the extent of this property is measured through the Pauling scale, which ranges from 0.7 to 4. The magnitude of electronegativity difference between atoms in a covalent bond influences the overall polarity of the bond.

The extent of polarity and bond strength in covalent bonds increases with a greater difference in electronegativity between the atoms involved. Consequently, polar covalent bonds exhibit an intermediate level of bond strength.

Properties of Polar Covalent Bond

Polar covalent bonding is observed when two nonmetals or between a nonmetal and a metalloid engage in the sharing of electrons.
This type of bonding is characterized by an unequal distribution of electrons within the compound.
The electronegativity difference between the atoms involved typically ranges between 0.1 and 2.
A polarity arises in the bond, resulting in one end being positively charged and the other end being negatively charged.
Notably, polar compounds exhibit solubility in polar solvents, a phenomenon driven by the attractive forces between molecules with opposite charges.

Examples of Polar Covalent Bond

Water (

$H_2O$ ):

Water is a polar solvent. A polar covalent bond forms due to the oxygen (O) atom's higher electronegativity compared to hydrogen. The shared electrons are pulled closer to oxygen, resulting in a partial negative charge on the oxygen atom. Conversely, the hydrogens (H), essentially protons, carry a partial positive charge.

Hydrogen Chloride (HCl):

Hydrogen chloride is a polar covalent compound wherein the chlorine (Cl) atom, possessing higher electronegativity than hydrogen (H), imparts a partial negative charge to itself. Simultaneously, hydrogen carries a partial positive charge.

Ammonia ( $NH_3$ ):

Ammonia is a polar molecule composed of a central nitrogen (N) atom bonded to three hydrogen (H) atoms. Due to nitrogen's higher electronegativity, the electrons tend to concentrate around the nitrogen atom, resulting in a polar configuration for the molecule.

Nonpolar Covalent Bond

In a nonpolar covalent bond, electrons are evenly shared between two atoms. This occurs when there is no difference in electronegativities between the participating atoms.

Properties of Nonpolar Covalent Bond

Occurs between two identical nonmetals.It involves the equal sharing of electrons.
It is characterized by an electronegativity difference of 0 between the atoms.
Nonpolar compounds exhibit solubility in nonpolar solvents, and their physical states are typically apparent as liquids or gases at room temperature.

Examples of Nonpolar Covalent Bond

Hydrogen (

$H_2$ )

Consider a hydrogen molecule (

$H_2$ ) to illustrate this concept. Given that the nuclei of each hydrogen (H) atom contains protons, the electrons within the bond are drawn toward these nuclei. In the context of a single covalent bond involving two H atoms, the symmetry of the situation ensures that each nucleus exerts an identical force on the shared electrons. Consequently, the electron pair is distributed equally between the two hydrogen atoms.

Examples of Nonpolar Covalent Molecules with Polar Covalent Bond

Certain nonpolar molecules consist of polar covalent bonds. Within these molecules, the arrangement of the individual polar bonds is structured in a manner that results in the cancellation of their respective polarities.

Carbon dioxide (

$CO_2$ )

Consider the case of a carbon dioxide (

$C0_2$ ) molecule. Within this arrangement, a central carbon atom forms double bonds (C=O) with two oxygen atoms, resulting in a linear molecular structure with a 180-degree angle between the oxygen atoms. Electrons are not shared equally between the two atoms due to the electronegativity difference. However, the molecule's symmetrical and linear configuration leads to the cancellation of individual bond polarities. Consequently, carbon dioxide is identified as a nonpolar molecule due to the balanced nature of its molecular arrangement.

Summary

A covalent bond tends to be polar when the sharing of electrons is unequal between the participating atoms.
This asymmetry in electron sharing is a consequence of the variance in electronegativities exhibited by the two atoms involved in the bond.
Electronegativity quantifies an atom's tendency to attract a shared pair of electrons, and the extent of this property is measured through the Pauling scale, which ranges from 0.7 to 4.
In a nonpolar covalent bond, electrons are evenly shared between two atoms. This occurs when there is no difference in electronegativities between the participating atoms.

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