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Explain Bohr's atomic model. |
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Answer» Solution :Bohr in 1913, concluded that in spite of the success of electromagnetic theory in explaining large scale phenomena it could not be applied to the processes at the atomic scale. Concepts that are different from the classical mechanics and electromagnetism would be needed to understand the structure of atoms and the relation of atomic structure to atomic spectra. Bohr combined classical and early quantum concepts and gave his theory in the form of three postulates they are as follows: (1) An electron in an atom could revolve in certain stable orbits without the emission of radiant energy, contrary to the predication of electromagnetic theory. According to this postulate, each atom has certain definite stable states in which it can exist and each possible state has definite total energy. These are called the stationary states of the atom. (2) The electron revolves AROUND the nucleus only in those orbits for which the ANGULAR MOMENTUM is some integral MULTIPLE of `(h)/(2pi)` where h is the planks.s constnat `(=6.6xx10^(-34))`. Thus the angular momentum (1). of the ORBITING electron is quantised. That is `L=(nh)/(2pi)=mvr` Bohr.s third postulate incorporated into atomic theory the early quantum concepts that had been developed by Planck and Einstein. It state that an electron might make a transition from one of its specified nonradiating orbits to another of lower energy. When it does so, a photon is emitted having energy equal to the energy difference between the initial and final states. The frequency of the emitted photon is `hv=E_(i)-E_(f)` `:.v=(E_(i)-E_(f))/(h)` where v= frequency of photon `E_(i)`= energy of initial state and `E_(f)=` energy of initial state and`E_(i) gt E_(f)`. |
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