In the field of atomic physics, Rutherford-Bohr model or Bohr diagram or simply Bohr model was given by Neils Bohr and Ernest Rutherford, in 1913. The model depicts the atom as a positively charged small nucleus which is surrounded by electrons travelling in circular orbits around the nucleus with electrostatic forces providing a source of attraction.
FEATURES OF BOHR’S ATOMIC MODEL
- Electrons revolve in stable orbits around the nucleus. There is no emission of radiant energy. Every orbit has a definite energy called energy shell or energy level.
- An energy level or orbit has been designated as the K, L, M, N shell. An electron is said to be in its ground state when it is in the lowest energy level.
- While jumping from one orbit or energy level to another, the electron either emits or absorbs energy. When the electron jumps from energy shell with higher energy to a energy shell of lower energy, the electron emits energy. But when the electron jumps from the lower energy level to the higher energy level, the electron absorbs energy.
- The energy that is absorbed or emitted by the electron is equal to the difference between the energies of the two energy level (E1, E2), which is later determined by the Plank’s equation.
⩟E= E2- E1= hv
⩟E is equal to the energy emitted or absorbed
H is the Plank’s constant
V is the frequency of the electromagnetic radiation that is emitted or absorbed
- The angular momentum of an electron that revolves around the energy shell is given by-
N is the number of energy shells
is the mass of electron
R is radius
And h is the Plank’s constant
LIMITATIONS OF BOHR’S ATOMIC MODEL
- The model failed to explain the Zeeman Effect which is the effect of the magnetic field on the spectra of atoms.
- The model could not explain the Stark Effect even which is the effect of the electric field on the spectra of atoms.
- The model also is a violation of the Heisenberg Uncertainty Principle. According to Heisenberg, it is impossible for an electron to have a known radius along with a known orbit i.e. known position and the momentum. But, Bohr’s model states that only.
- The model could make accurate predictions for the smaller sized atoms like Hydrogen, but it failed to make predictions for larger atoms.