Question

State postulates of Bohr’s atomic model.

Hint:

Bohr’s model introduced the concept of quantized orbits, which was crucial in explaining the spectral lines observed in atomic spectra.

Answer 1

Step 1: Stationary Orbits.
In Bohr’s model, electrons are restricted to certain fixed orbits or energy levels around the nucleus. These orbits do not radiate energy despite the motion of the electron.
Step 2: Quantization of Angular Momentum.
Bohr postulated that the angular momentum of an electron in these stable orbits is quantized and given by: \[ L = n \hbar \] where \( n \) is a positive integer (quantum number), and \( \hbar \) is the reduced Planck’s constant.
Step 3: Emission and Absorption of Radiation.
When an electron jumps from a higher orbit to a lower one, it emits radiation with energy \( E = E_{\text{higher}}
- E_{\text{lower}} \). Similarly, when an electron absorbs energy, it moves to a higher orbit.
Step 4: Conclusion.
Bohr’s postulates explain the discrete nature of electron energy levels and the emission or absorption of radiation in discrete quantities.