Question

Evaluate the Bohr model of the atom. 

(a) What two key features of the atom did the Bohr model fail to explain? 

(b) How did quantum theory explain these features?

Answer 1

Part A) Bohr atom model is not able to explain the below mentioned key features of an atom

1. The Bohr atomic theory considered that electrons have both a well-defined radius or orbit i.e. known position and momentum at the same time, which is impossible according to the Heisenberg Uncertainty Principle.
2. Bohr's theory failed to explain the Zeeman effect when the spectral line is split into several components in the presence of a magnetic field and the Stark effect when the spectral line gets split up into fine lines in the presence of an electric field.

Part B) In quantum theory

1. In quantum theory, the behavior of electrons within atoms is explained by treating them mathematically as matter waves as per de-Broglie hypothesis. And in Quantum theory we introduced the concept of electron cloud instead of well-defined orbit.
2. The splitting of spectral lines in the presence of an external electric or magnetic field will be explained as the change in the energy level of the electron a charged particle in the presence of an external field.