Question 6: Why Bohr extends quantum theory to the structure of atom?
Rutherford proposed atomic model in 1911. It suggests the electrons are moving around the nucleus like the planets move around the sun in the solar system.
Classical theory fails to explain this sort of motion of electron. Because classical theory assumes an accelerated charged particle emits energy continuously. So the electron, being a charged particle, will emit energy continuously and following a spiral path it will collapse into the nucleus. However, it does not happen.
Two years later, in 1913, Bohr extended Quantum theory to Rutherford atomic model and said that the electron revolves around the quantized energy states. As far as, the electron is in its quantized energy state, it does not emit energy. Electron emits or absorbs energy only when it jumps from one energy state to another. This enabled us to explain the revolving of electron around the nucleus.