The key difference between ionization energy and binding energy is that ionization energy is the minimum amount of energy needed to remove the most loosely bound electron of an isolated neutral gaseous atom or molecule whereas binding energy is the minimum amount of energy required to remove a particle from a system of particles.
Ionization energy and binding energy of chemical systems are two different terms, describing two different phenomena. Let us discuss more details below in this article.
CONTENTS
1. Overview and Key Difference
2. What is Ionization Energy
3. What is Binding Energy
4. Side by Side Comparison – Ionization Energy vs Binding Energy in Tabular Form
5. Summary
What is Ionization Energy?
Ionization energy is the minimum amount of energy needed to pull away the most loosely bound electron of an isolated neutral gaseous atom or molecule. We can denote this ionization reaction as follows:
X(g) + energy ⟶ X+(g) + e–
In this equation, X is any atom or molecule while X+ is the ion with the loosely bound electron removed from the atom or molecule while e– is the removed electron. Generally, this is an endothermic process. Typically, farther the outermost electron is from the atomic nucleus, lower the ionization energy and vice versa.
Figure 01: First Ionization Energy trends in the Periodic Table of Elements
In physical chemistry, ionization energy is expressed in the unit of electronvolts (eV). However, this unit is not usually used in chemical terms because we calculate the values “per mole” units. Therefore, the unit of measurement of ionization energy is kilojoules per mole (kJ/mol). Moreover, there are periodic trends of ionization energy in the periodic table; ionization energy usually increases from left to right within a given period, and ionization energy generally decreases from top to bottom in a given group.
What is Binding Energy?
Binding energy is the minimum amount of energy required to remove a particle from a system of particles. We can also describe it as the smallest amount of energy required to disassemble a system of particles into individual parts. However, in nuclear physics, the term separation energy is used rather than the term binding energy. Typically, a bound system is at a lower energy level than its unbound constituents.
Figure 02: Binding Energy Curve for Different Chemical Elements
There are different types of binding energy: electron binding energy or the ionization energy, atomic binding energy, bond dissociation energy, nuclear binding energy, gravitational binding energy, etc.
What is the Difference Between Ionization Energy and Binding Energy?
Ionization energy is a type of binding energy. The key difference between ionization energy and binding energy is that the ionization energy is the minimum amount of energy needed to detach the most loosely bound electron of an isolated neutral gaseous atom or molecule whereas the binding energy is the minimum amount of energy required to remove a particle from a system of particles.
Below is a summary of the difference between ionization energy and binding energy.
Summary – Ionization Energy vs Binding Energy
Ionization energy is a type of binding energy. The key difference between ionization energy and binding energy is that ionization energy is the minimum amount of energy needed to remove the most loosely bound electron of an isolated neutral gaseous atom or molecule whereas binding energy is the minimum amount of energy required to remove a particle from a system of particles.
Reference:
1. “Binding Energy.” Wikipedia, Wikimedia Foundation, 20 Sept. 2020, Available here.
2. “Ionization Energy.” Chemistry LibreTexts, Libretexts, 21 Aug. 2020, Available here.