The key difference between Bohr and Schrodinger model is that in the Bohr model, electrons are particles that occupy only certain orbits of fixed energy around the nucleus, whereas, in the Schrodinger model, electrons behave as standing waves having a greater probability of being in some areas of space compared to others.
Bohr model and Schrodinger model are very important models in chemistry as they describe the chemical structure of atoms and the location of electrons at a given time.
CONTENTS
1. Overview and Key Difference
2. What is Bohr Model
3. What is Schrodinger Model
4. Bohr vs Schrodinger Model in Tabular Form
5. Summary – Bohr vs Schrodinger Model
What is Bohr Model?
Bohr model, which is a modification of the Rutherford model, explains the structure of the atom as composed of a nucleus surrounded by electrons. However, the Bohr model is highly advanced than the Rutherford model since it suggests that electrons always travel in specific shells or orbits around the nucleus. This model also states that these shells have different energies and are spherical in shape. This phenomenon was suggested by observations of the line spectra for the hydrogen atom.
Since there are discrete lines in the line spectra, Bohr stated that the orbitals of an atom have fixed energies, and electrons can jump from one energy level to the other emitting or absorbing energy, resulting in a line in the line spectra.
Figure 01: Bohr Model
Main Postulates of the Bohr Model
- The electrons move around the nucleus in spherical orbitals, which have a fixed size and energy.
- Each orbit has a different radius and is named from the nucleus to the outside as n=1, 2, 3, etc., or n= K, L, M, etc., where n is the fixed energy level number.
- The energy of an orbital is related to its size.
- The smallest orbit has the lowest energy. The atom is completely stable when electrons are at the lowest energy level.
- When an electron is moving in a certain orbital, the energy of that electron is constant.
- Electrons can move from one energy level to another by absorbing or releasing energy.
- This movement causes radiation.
Generally, Bohr’s model perfectly fits the hydrogen atom, which has a single electron and a small positively charged nucleus. Apart from that, Bohr used Plank’s constant to calculate the energy of the energy levels of the atom.
But there were a few drawbacks of the Bohr model when explaining the atomic structure of atoms other than Hydrogen.
Limitations of the Bohr Model
- The Bohr model could not explain the Zeeman effect (effect of magnetic field on the atomic spectrum).
- It could not explain the Stark effect (effect of electric field on the atomic spectrum).
- Bohr model fails to explain the atomic spectra of larger atoms.
What is Schrodinger Model?
Schrodinger model is a model in chemistry that assumes that an electron is a wave. This model describes regions in space or orbitals as locations where electrons are most likely to occur. This is a powerful model of the atom that was developed by Erwin Schrodinger in 1926. He combined the equations for the behavior of waves and the de Broglie equation in order to create a mathematical model to describe the distribution of electrons in an atom.
Figure 02: Wave Function as described by Schrodinger
The major advantage of Schrodinger model is that it contains mathematical equations known as wave functions, which can satisfy the need for places on the behavior of electrons. However, it can be difficult to imagine a physical model for electrons as waves. Rather than trying to tell where the electron is at any time, this model describes the probability of an electron being found in a given region of space at a given time.
What is the Difference Between Bohr and Schrodinger Model?
Bohr model and Schrodinger model are like the basics of general chemistry. The key difference between Bohr and Schrodinger model is that in the Bohr model, electrons are particles that occupy only certain orbits of fixed energy around the nucleus, whereas, in the Schrodinger model, electrons behave as standing waves having a greater probability of being in some areas of space compared to others.
Below is a summary of the difference between Bohr and Schrodinger model in tabular form for side by side comparison.
Summary – Bohr vs Schrodinger Model
Both the Bohr model and Schrodinger model describe the chemical structure of atoms and the location of electrons at a given time. The key difference between Bohr and Schrodinger model is that in the Bohr model, electrons are particles that occupy only certain orbits of fixed energy around the nucleus, whereas, in the Schrodinger model, electrons behave as standing waves having a greater probability of being in some areas of space compared to others.
Reference:
1. “Schrodinger Model.” Erwin Schrodinger, Purdue Education.
Image Courtesy:
1. “Bohr model” By Jia.liu – Own work (Public Domain) via Commons Wikimedia
2. “Wavepacket-a2k4-en” By Xcodexif – Own work (CC BY-SA 4.0) via Commons Wikimedia
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