The key difference between protonation and ionization is that protonation is the addition of a proton to a chemical species, whereas ionization is the removal or obtaining of electrons from chemical species.
Protonation and ionization are two chemical concepts that are important in describing the ionic behaviour of chemical species.
CONTENTS
1. Overview and Key Difference
2. What is Protonation
3. What is Ionization
4. Side by Side Comparison – Protonation vs Ionization in Tabular Form
5. Summary
What is Protonation?
Protonation is the addition of a proton to a chemical species such as an atom, molecule, or ion. This forms the conjugate acid of the corresponding chemical species. Protonation can be described as a fundamental chemical reaction, and it is an important step in many stoichiometric and catalytic processes.
Figure 01: A Protonation Reaction
There are two types of protonation processes known as monobasic protonation and polybasic protonation. Monobasic protonation is the single protonation that takes place in some ions and molecules. But in some ions and molecules, there can be more than one protonation, and we can name them as polybasic chemical species. This polybasic nature it true for many biological macromolecules.
What is Ionization?
Ionization is a chemical process in which atoms or molecules get a positive or negative charge. This process occurs due to either removing or obtaining electrons from atoms or molecules, respectively. In the ionization process, we can name the resulting ions as anions and cations, depending on the charge they have, i.e. cations are positively charged ions and anions are negatively charged ions. Basically, the loss of electrons from a neutral atom or a molecule forms a cation, and the gain of electrons from a neutral atom gives it a negative charge, forming an anion.
When an electron is removed from a neutral gaseous atom by the addition of energy, it forms a monovalent cation. This is because a neutral atom has equal numbers of electrons and protons, resulting in no net charge; when we remove an electron from that atom, there is one excess proton that lacks an electron to neutralize its charge. Therefore, that atom gets a +1 charge (it is the charge of the proton). The amount of energy required for this is the first ionization energy of that atom.
Figure 02: Ionization Reaction
Besides, the ionization that takes place in a liquid solution is the formation of ions in the solution. For example, when HCl molecules dissolve in water, hydronium ions (H3O+) are formed. Here, HCl reacts with water molecules and forms positively charged hydronium ions and negatively charged chloride (Cl–) ions.
Furthermore, ionization may occur through collisions. But this type of ionization occurs mainly in gases when an electric current pass through the gas. If the electrons in the current have a sufficient amount of energy required to remove electrons from gas molecules, they will force out electrons from gas molecules, producing ion pairs that consist of the individual positive ion and the negative electron. Here, negative ions also form because some electrons tend to attach to gas molecules rather than pulling electrons out.
Moreover, ionization occurs when radiation energy or sufficiently energetic charged particles pass through solids, liquids or gases; for example, alpha particles, beta particles, and gamma radiation can ionize substances; therefore, we name them ionizing radiation.
What is the Difference Between Protonation and Ionization?
Protonation and ionization are important chemical concepts in chemistry. The key difference between protonation and ionization is that protonation is the addition of a proton to a chemical species, whereas ionization is the removal or obtaining of electrons from chemical species.
The below infographic summarizes the differences between protonation and ionization in tabular form.
Summary – Protonation vs Ionization
Protonation and ionization are opposite to each other because protonation refers to addition while ionization refers mostly to bond breaking. The key difference between protonation and ionization is that protonation is the addition of a proton to a chemical species, whereas ionization is the removal or obtaining of electrons from chemical species.
Reference:
1. “Ionization.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., Available here.
Image Courtesy:
1. “Protonation d’un alcool tertiaire” By The original uploader was Rhadamante at French Wikipedia. – Transferred from fr.Wikipedia to Commons by Bloody-libu using CommonsHelper. (CC BY-SA 3.0) via Commons Wikimedia
2. “Ionization reaction” By Cseizert – Own work (CC BY-SA 3.0) via Commons Wikimedia