Protonation Definition and Example

Chemistry Glossary Definition of Protonation

Illustration of an atom
Protonation is similar to hydrogenation, except since only the proton is added (not the electron), the net charge of a protonated species increases by +1. Tony Stone Images / Getty Images
By
Anne Marie Helmenstine, Ph.D.
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.
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Updated on July 03, 2019

Protonation is the addition of a proton to an atom, molecule, or ion. Protonation is different from hydrogenation in that during protonation a change in charge of the protonated species occurs, while the charge is unaffected during hydrogenation.

Protonation occurs in many catalytic reactions. Both protonation and deprotonation occur in most acid-base reaction. When a species is either protonated or depronated, its mass and charge change, plus its chemical properties are altered. For example, protonation may change the optical properties, hydrophobicity, or reactivity of a substance. Protonation is usually a reversible chemical reaction.

Protonation Examples

  • An example is the formation of the ammonium group where NH4+ is formed by protonation of ammonia NH3
  • Water may be protonated by sulfuric acid:
    H2SO4 + H2O ⇌ H3O+ + HSO-4 
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Helmenstine, Anne Marie, Ph.D. "Protonation Definition and Example." ThoughtCo, Aug. 26, 2020, thoughtco.com/definition-of-protonation-604621. Helmenstine, Anne Marie, Ph.D. (2020, August 26). Protonation Definition and Example. Retrieved from https://www.thoughtco.com/definition-of-protonation-604621 Helmenstine, Anne Marie, Ph.D. "Protonation Definition and Example." ThoughtCo. https://www.thoughtco.com/definition-of-protonation-604621 (accessed March 28, 2023).