Difference Between Covalent and Polar Covalent

Main Difference – Covalent vs Polar Covalent

There are different types of chemical bonds in compounds. Covalent bonds are such chemical bonds. A covalent bond is formed when two atoms share their unpaired electrons with each other. Keeping unpaired electrons is not a stable state for an atom. Therefore, they form covalent bonds in order to obey the electron configuration around the atom. Covalent bonds can be either polar or nonpolar. The main difference between covalent and polar covalent is that a covalent bond can be either polar or nonpolar whereas a polar covalent bond is essentially polar.

Key Areas Covered

1. What is Covalent
      – Definition, Octet Rule, Different Types
2. What is Polar Covalent
      – Definition, Electronegativity
3. What is the Difference Between Covalent and Polar Covalent
     – Comparison of Key Differences

Key Terms: Chemical Bond, Covalent Bond, Covalent Compound, Electronegativity, Nonpolar, Octet Rule, Pi Bond, Polar Covalent Bond, Sigma Bond

What is Covalent

The term covalent is used to name chemical bonds formed by sharing unpaired electrons between atoms or to name compounds composed of atoms bonded to each other via covalent bonds. Covalent bonds are formed when two atoms share their unpaired electrons with each other in order to obtain a stable electron configuration.

According to the octet rule of electronic configuration, an atom other than hydrogen tends to form bonds until it is surrounded by eight valence electrons. Hence, atoms form either ionic bonds or covalent bonds in order to obey the octet rule.

When a covalent bond is formed, the two electrons are shared by both atoms. For example, a carbon atom in ground state has four valence electrons (Valence electrons are electrons that are located in the outermost orbital of an atom). In order to complete the electron configuration, carbon atom shares its four electrons with another four electrons (unpaired). The simplest example is methane. In methane, four hydrogen atoms share their unpaired electrons with one carbon atom, forming four covalent bonds.

Figure 1: Four Covalent Bonds in Methane Molecule

A covalent compound is a chemical compound that is composed of atoms bonded to each other via covalent bonds. These compounds can be molecules or ions. A covalent bond can be either polar or nonpolar. Covalent bonds can also be single bonds, double bonds or triple bonds. A single bond is a sigma bond. Double and triple bonds are composed of pi bonds along with a sigma bond.

What is Polar Covalent

The term polar covalent is used to name a covalent bond that is polar. There are two types of covalent bonds as polar covalent bonds and nonpolar covalent bonds. Nonpolar covalent bonds are formed when two atoms share equal electron pairs. A polar covalent bond is formed when two atoms share unequal distribution of electrons.

The unequal electron distribution causes the covalent bond to have a slight electrical charge separation. Then one end of the covalent bond has a delta positive electrical charge and the other end will have a delta negative charge. This is known as a dipole moment.

Figure 2: Polar Covalent Bonds in Water Molecule

The reason for this unequal electron distribution between two atoms is the difference between the electronegativity values of atoms. When two atoms with different electronegativities are in a covalent bond, the bond electrons are more attracted towards the more electronegative atom than the other atom. For example, a covalent bond between C and O will show a delta positive charge on the carbon atom and a delta negative charge on the oxygen atom. This is because the electronegativity of O is 3.44 and for carbon, it is 2.55.

Difference Between Covalent and Polar Covalent

Definition

Covalent: The term covalent refers to chemical bonds formed by sharing unpaired electrons between atoms or to compounds composed of atoms bonded to each other via covalent bonds.

Polar Covalent: The term polar covalent is used to name a covalent bond that is polar.

Polarity

Covalent: Covalent bonds can be either polar or nonpolar.

Polar Covalent: Polar covalent bonds are polar.

Electrical Charge Separation

Covalent: Covalent bonds may or may not have electronic charge separation.

Polar Covalent: Polar covalent bonds show a slight electrical charge separation.

Dipole Moment

Covalent:  Covalent may or may not show a dipole moment.

Polar Covalent: Polar covalent bonds show a dipole moment.

Conclusion

A covalent bond is formed when two atoms share their unpaired electrons with each other. Covalent bonds can be either polar or nonpolar. The main difference between covalent and polar covalent is that a covalent bond can be either polar or nonpolar whereas a polar covalent bond is essentially polar.

References:

 1. Helmenstine, Anne Marie. “Understand What a Covalent Bond Is in Chemistry.” ThoughtCo, Available here.
2. Helmenstine, Anne Marie. “What’s a Polar Bond in Chemistry? Definition and Examples.” ThoughtCo, Available here.

Image Courtesy:

1. “Covalent” By DynaBlast – Created with Inkscape (CC BY-SA 2.5) via Commons Wikimedia
2. “209 Polar Covalent Bonds in a Water Molecule” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia