Limitations of Bohr’s Model

The Bohr model was introduced by the famous physicist Niels Bohr in 1913. Bohr’s model is based on the assumption that the nucleus is surrounded by the electrons which travel in a circular orbit around the nucleus. Bohr’s atomic model Explain that How electrons revolve around the nucleus in specific Energy shells. It explains some of the infinite  specific energy shells around the K,L,M,N….in which electrons revolve and this is the advantage of Bohr’s model. There are certain limitations of Bohrs model, such as its inability to provide sufficient information and explanation for atoms other than the smaller ones, etc. The drawbacks and advantages of Bohr model are discussed further. 

Development of the Model

The Bohr model helps in understanding the behaviour of atoms and subatomic particles. The model proposed by Bohr relied on Planck’s quantum theory of radiation. Bohr’s model improved the earlier proposed models, such as the Saturnian model and the Rutherford model.  

The Rutherford model had certain limitations, which Bohr and justification rectified was provided by him. Factors such as the dual nature of electromagnetic radiation, which states that radiations possess both wavelike and particle-like characteristics, black body radiation and the photoelectric effects led to the development of Bohr’s model. Earlier models had experimental validation, whereas Bohr provided theoretical and empirical results. The Bohr model is prominent today due to its simplicity and accurate results.  

Electron’s Property under This Model  

The properties of electrons mentioned in Bohr’s model are – 

• The electrons move/ revolve around the nucleus in definite orbits known as discrete orbits to overcome the loss of energy. Electrons revolve around the nucleus without radiating any energy in orbits known as ‘Stationary orbits’. 
• Each orbit is associated with a specific amount of energy, and these orbits are called shells or energy levels. Energy is radiated from the electrons when they move from the higher energy level to the lower energy level. The assumption here was that the orbits are planar, and this was one such area that suffered from certain limitations of Bohr’s model theory. 
• Similarly, the electrons absorb energy when they move from the lower energy level to the higher energy level. This state is known as the excited state. 
• Orbits closer to the nucleus with lower energy levels are more stable than the far orbits. The electrons in the lowest orbit are said to be in the ground state. 

There are both advantages as well as limitations of Bohr’s model theory :-

Advantages of Bohr’s Model 

There are both advantages as well as limitations of Bohr’s model theory. 

The advantages are –

• The Bohr model explained the stability of atoms and the concept of the stationary state of an electron, in which he explains the gain and loss of energy by the electrons. The electrons cannot lose energy when moving in a particular orbit. Therefore, there is no emission of radiation and thus no instability. 
• It was able to justify the line spectrum of hydrogen and single-electron ions like He+ and Li2+.
• Offered a basis for calculating the energy of electrons in hydrogen atoms and similar compounds. 

Limitations of Bohr’s Model 

• One of the limitations of the Bohr model is that it could not explain the splitting of spectral lines when they split into closely placed lines under the influence of an electric field (Stark effect) and a magnetic field (Zeeman Effect). It failed to explain the ability of atoms to form molecules through chemical bonds.
• In the Bohr plan, the electrons revolving around the nucleus are considered on a planar dimension. This is one of the biggest limitations of Bohrs model. It was later revealed that the dimension in which the electron moves around the nucleus is three dimensional. 
• The biggest limitation of Bohr’s model was that it failed to make correct predictions of large-sized atoms and explain the spectrum of atoms having only two electrons, such as the helium atom. 
• The primary focus was on hydrogen, another limitation of the Bohr model. Furthermore, it violated Heisenberg’s Principle. This principle states that it is impossible to determine electrons’ accurate position and momentum simultaneously. In the Bohr’s model, the electrons revolve in a well-defined circular orbit. 

Conclusion 

Although the Bohr model provided proper justifications for the previously proposed models and served as a basis for several justifications and theories, it suffered from certain limitations. The limitations of Bohrs model include limitations such as focusing only on hydrogen inability to explain the splitting of lines. It violated Heisenberg’s Principle, and mainly the whole assumption was flawed as it was based on the idea of a planar dimension. Such factors were criticised as some of the crucial limitations of Bohrs model.