Know the Difference Between Ionic and Covalent Bonds (2024)

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Know the Difference Between Ionic and Covalent Bonds (1)

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Anne Marie Helmenstine, Ph.D.

Chemistry Expert

Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
B.A., Physics and Mathematics, Hastings College

Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.

Ionic Bonds

In an ionic bond, one atom essentially donates an electron to stabilize the other atom. In other words, the electron spends most of its time close to the bonded atom.Atoms that participate in an ionic bond have different electronegativity values from each other. A polar bond is formed by the attraction between oppositely charged ions.For example, sodium and chloride form an ionic bond, to make NaCl, or table salt. You can predict an ionic bond will form when two atoms have different electronegativity values and detect an ionic compound by its properties, including a tendency to dissociate into ions in water.

Covalent Bonds

In a covalent bond, the atoms are bound by shared electrons. In a true covalent bond, the electronegativity values are the same (e.g., H₂, O₃), although in practice the electronegativity values just need to be close. If the electron is shared equally between the atoms forming a covalent bond, then the bond is said to be nonpolar. Usually, an electron is more attracted to one atom than to another, forming a polar covalent bond. For example, the atoms in water, H₂O, are held together by polar covalent bonds. You can predict a covalent bond will form between two nonmetallic atoms. Also, covalent compounds may dissolve in water but don't dissociate into ions.

Ionic vs. Covalent Bonds Summary

Here's a quick summary of the differences between ionic and covalent bonds, their properties, and how to recognize them:

	Ionic Bonds	Covalent Bonds
Description	Bond between metal and nonmetal. The nonmetal attracts the electron, so it's like the metal donates its electron to it.	Bond between two nonmetals with similar electronegativities. Atoms share electrons in their outer orbitals.
Polarity	High	Low
Shape	No definite shape	Definite shape
Melting Point	High	Low
Boiling Point	High	Low
State at Room Temperature	Solid	Liquid or Gas
Examples	Sodium chloride (NaCl), Sulfuric Acid (H₂SO₄ )	Methane (CH₄), Hydrochloric acid (HCl)
Chemical Species	Metal and nonmetal (remember hydrogen can act either way)	Two nonmetals

Test Your Knowledge of Ionic and Covalent Bonds

Think you fully understand the differences between ionic and covalent bonds? Test your comprehension with this 10-question quiz.

Ionic vs. Covalent Bonds

The two main types of chemical bonds are ionic and covalent bonds.
An ionic bond essentially donates an electron to the other atom participating in the bond, while electrons in a covalent bond are shared equally between the atoms.
The only pure covalent bonds occur between identical atoms. Usually, there is some polarity (polar covalent bond) in which the electrons are shared, but spend more time with one atom than the other.
Ionic bonds form between a metal and a nonmetal. Covalent bonds form between two nonmetals.

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