Explain why the Bohr model is more acceptable than the Rathford model of the atom.

Question: Which one is more acceptable between Rutherford’s atomic model and Bohr’s atomic model? Analyze.

Major Postulates of Rutherford’s Atomic Model:

• a. There is a positively charged dense core at the center of the atom, called the nucleus.
• b. Negatively charged particles, called electrons, are constantly revolving around the nucleus of the atom.
• c. The number of positively charged protons inside the nucleus is exactly equal to the number of revolving negatively charged electrons outside the nucleus. Therefore, the atom is electrically neutral.
• d. The electrostatic force of attraction (centripetal force) existing between the nucleus and the electrons is equal and opposite to the centrifugal force generated due to the revolution of electrons.

Major Postulates of Bohr’s Atomic Model:

• a. Concept of stationary orbits or fixed energy levels: Electrons revolve only in certain permitted, non-radiating circular paths around the nucleus.
• b. Concept of angular momentum of electrons: The angular momentum ($mvr$) of a revolving electron is quantized and is an integral multiple of $\frac{h}{2\pi}$.
• c. Concept of energy absorption, emission, and spectrum formation: Energy is absorbed or emitted only when an electron jumps from one energy level to another, which leads to the formation of atomic spectra.

Comparative Analysis of Rutherford’s and Bohr’s Models:

An evaluation of the postulates of both models highlights the following critical insights and differences:

1. Rutherford’s model fails to explain the origin of **atomic spectra**, whereas Bohr’s model provides a successful theoretical explanation for the spectral lines of hydrogen-like systems.
2. No definite idea regarding the **size and shape** of electron orbits can be obtained from Rutherford’s model, but Bohr’s model explicitly introduces circular orbits of fixed radius.
3. The concept of different types of radiation resulting from the **transition of electrons** between distinct energy levels is entirely absent in Rutherford’s model, but it is a cornerstone of Bohr’s model.
4. Rutherford’s model gives no indication about the **angular momentum** of electrons, while Bohr’s model successfully quantizes it using the formula $mvr = \frac{nh}{2\pi}$.
5. Unlike Rutherford’s model, Bohr’s model enables the mathematical calculation of the **radius of an orbit, velocity of an electron, energy of a shell**, and the frequency of the lines generated in the spectrum.
6. According to Maxwell’s electromagnetic theory, Rutherford’s model cannot explain the **stability of an atom** (as the electron should spiral into the nucleus), whereas Bohr’s model successfully accounts for atomic stability by proposing non-radiating stationary states.