What is Bohr’s Model of an Atom? – Diagram, Applications, Limitations

What is Bohr’s Atomic Model?

Neil Bohr proposed the Bohr model in 1915. It was developed by a modification to Rutherford’s atomic model. Rutherford’s concept established the nuclear model of an atom, in which a positively charged nucleus is surrounded by negatively charged electrons. Thomson’s and Rutherford’s atomic models failed to answer any queries about an atom’s energy and stability. 

The atomic structure model was amended by Bohr’s theory, which indicated that electrons travel in fixed orbitals (shells) and not everywhere in between, and that each orbit (shell) has a fixed energy. Rutherford described an atom’s nucleus, and Bohr expanded on that concept to include electrons and their energy levels. 

Diagram of Bohr’s Model

Postulates of Bohr’s Model

• In an atom, electrons (negatively charged particles) rotate around the positively charged nucleus in a predetermined circular route known as orbits or shells. 
• Each orbit or shell has a predetermined energy, and these circular orbits are referred to as orbital shells. 
• The quantum number n=1, 2, 3… represents the energy levels. This quantum number range series is on the nucleus side, with n=1 starting with the lowest energy level. The orbits n=1, 2, 3, 4… are designated as K, L, M, N…. shells, and an electron is said to be in the ground state when it reaches the lowest energy level. 
• Electrons in an atom gain energy to go from a lower energy level to a higher energy level, and electrons lose energy to move from a higher energy level to a lower energy level. 

Limitations of Bohr’s Atomic Model

• The Zeeman impact (the impact of a magnetic field on the spectra of atoms) was not explained by Bohr’s concept of an atom. 
• It also failed to explain the Stark effect (the impact of an electric field on atom spectra). 
• It contradicts the Heisenberg Uncertainty Principle. 
• It couldn’t account for the spectra observed from bigger atoms. 

Applications of Bohr’s Model of an Atom

• Bohr’s theory applies to hydrogen-like substances with only one electron, such as Li2+.  Each Li2+ and H-atom has only one electron. He and He2+ have two and zero electrons, respectively. 

Final Notes

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FAQ

How many numbers of Electrons are present in K, L, M, and N Shells? 

The maximum number of electrons in the shells K, L, M, and N are 2, 8, 18, and 32, respectively.