limitations of Bohr’s Model of Atom

Bohr’s atomic model is the alteration of Rutherford’s atomic model, which appeared in 1915. It comprises a “little nucleus (positively charged)” encompassed by “negative electrons” moving around the nucleus in “orbits”. Bohr saw that an electron away from the centre has more energy, and electrons near the centre have less energy. 

As shown by this model, in an atom, the electrons turn around the core in clear energy levels called circles/shells. Per the model, the best number of electrons that can be obliged in a specific circle is 2n2, where n is the number of orbits. Additionally, the most outrageous number of electrons that can be obliged in the outermost shell of an atom is 8. Bohr gives several postulates regarding the theory of the atomic model and has limitations, such as this model violates the Heisenberg uncertainty principle. Also, “Bohr’s model” of an atom failed to explain the “Zeeman effect”.

Electrons are eager to higher energy levels by engrossing energy and get back to bring down energy levels by transmitting energy.

History of Bohr’s Atomic Model

After proposed nuclear models, such as “the cubic model” (1902), “Saturnian model” (1904), “plum-pudding model” (1904), and “Rutherford model” (1911), Bohr’s model emerged as an improvement. 

The Bohr model is primarily a quantum-material science modification of the Rutherford model based on classical physical science. The model could successfully make sense of the Rydberg recipe for nuclear hydrogen’s unearthly outflow lines. 

The Rydberg formula was only tentatively known before, and it had never been demonstrated, but the Bohr model effectively presented the hypothetical idea.

The model of the atom proposed later, based on planetary motion, had a couple of issues. In that model, the spinning movement of electrons was considered in a circle around a core as a charged atom moving in an electric field; notwithstanding, there was not an extremely clear justification for the way that the electron would twist into the core. Considering electron surge, this would address a continuum of frequencies being created since, as the electron moves closer to the core, it will move rapidly and will exude another repeat which was seen probably. These planetary models finally guessed all particles to be shaky due to the orbital decay, which was misleading, and Bohr’s model figured out the quirk.

Postulates of the model of the atom proposed by Bohr

Bohr’s First Postulate of Atomic Model: 

In a particle, electrons rotate near the nucleus in a few fixed round orbits (called stationary orbits). Electrons don’t produce energy that was normal from electrodynamics.

Bohr’s Second Postulate of Atomic Model: Stationary Orbits, the orbits wherein the precise force is the fundamental momentum of an electron, is a product of “h/2π”, where “h” is Planck’s constant.

Along these lines, the momentum “L” of it is quantised to spin electrons.

Numerically, 

L = mvr = nh/2π

where, n is number 1,2,3….. known as an essential quantum number.

Bohr’s Third postulate of the Atomic Model: The energy of an electron spinning in a stationary orbit stays steady. Energy is transmitted from a particle just when an electron bounces from the orbit of higher energy to the orbit having low energy.

Whenever it works out, a photon is restricted, whose energy is equivalent to the distinction of energy of two orbits. If Ei and Ej are the energies of orbits in the underlying and last circumstance, the recurrence of the photon discharged will be given by the accompanying condition.

hv=Ei-Ef

An electron might hop in a higher energy orbit by retaining energy from outside. In this condition, the energy of photons assimilated is hv=Ef-Ei

Limitations of Bohr’s Atomic Model  

The nuclear model appeared in 1915. He made sense of electrons and their circle in his hypothesis. But there are several limitations like “Bohr’s model of an atom” fails to explain the “Zeeman effect” and violates the “Heisenberg uncertainty principle”.

Notwithstanding, a few limitations were seen in Bohr’s Atomic Model. These are:

•Bohr’s model was applied only to the unimolecular systems.

•It could not explain the spectral line spectrum of Hydrogen Atoms.

•Bohr’s model of an atom failed to explain the “Zeeman Effect”. 

•It doesn’t make sense of the stark impact, i.e. the effect of an electric field on the spectrum of Hydrogen atoms.

•It violates the Heisenberg Uncertainty Principle.

•It couldn’t make sense that the spectra were from bigger particles.

Conclusion

Bohr’s atomic model transformed into the precursor of quantum mechanical models. This hypothesis of the nuclear model is pertinent to H-like species (single electron framework). The article covers the proposals and limitations like how Bohr’s model of an atom failed to explain the Zeeman effect, violates the Heisenberg Uncertainty Principle of this nuclear model and does not show the effect of an electric field on the spectrum of Hydrogen atoms. It is useful in understanding other nuclear models proposed by different researchers.