The key difference between energy level and energy band is that energy levels exist at the atomic level while energy bands exist at the molecular level.
The terms energy level and energy band are closely related to each other, but there are some differences between them. According to quantum physics, confined particles such as electrons have quantized energy (discrete values of energy). We call these discrete values as energy levels. On the other hand, energy band is a continuous combination of several energy levels.
CONTENTS
1. Overview and Key Difference
2. What is an Energy Level
3. What is an Energy Band
4. Side by Side Comparison – Energy Level vs Energy Band in Tabular Form
5. Summary
What is an Energy Level?
Energy level is a quantized energy value of an atom. An atom contains electrons that are in continuous movement around the atomic nucleus. These electrons have discrete energy values; thus, we say the energy is quantized. We call each quantized energy value an energy level.
Moreover, we can call an energy level an energy shell because it is a region where a certain electron can move around the atomic nucleus. We give names for each shell; the energy level that is closest to the atomic nucleus is K shell, the next one is L shell and so on. According to quantum physics, these are the principal energy levels denoted by “n”.
Figure 1: Energy Level Diagram
Each energy level contains a fixed number of electrons. For example, the first energy level can hold 2 electrons while the second one can hold 8, the third one can hold 18 and so on. Generally, the formula for finding the number of electrons in the nth energy level is 2(n)2.
What is an Energy Band?
Energy band is a continuous combination of energy levels of electrons in a molecule. Therefore this term is used mainly in molecular level explanations. When there are multiple atoms combined with each other to form a molecule, the electrons get placed in molecular orbitals. A molecular orbital is the type of orbital that is formed by the combination of two atomic orbitals.
Figure 2: Typical Arrangement of Energy Bands
Since the energy levels of atomic orbitals are so close, they can form a continuous energy band.
What is the Difference Between Energy Level and Energy Band?
Energy level is a quantized energy value of an atom. Energy band is a continuous combination of energy levels of electrons in a molecule. Hence, the key difference between energy level and energy band is that energy levels exist at the atomic level and energy bands exist at the molecular level. Moreover, energy levels are discrete values while energy bands are continuous. So, this is also a significant important difference between energy level and energy band.
Summary – Energy Level vs Energy Band
Energy level and energy band are two close terms that have slight differences. The key difference between energy level and energy band is that energy levels exist at the atomic level and energy bands exist at the molecular level.
Reference:
1. “Energy Level.” Wikipedia, Wikimedia Foundation, 1 Mar. 2019, Available here.
Image Courtesy:
1. “Energy level diagram-en” By Niall Jackson – William Crochot – own work, visio (CC BY-SA 4.0) via Commons Wikimedia