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Bohr's model of atom

Bohr's model of atom:
In 1913, niel bohr put forward a new theory of atomic structure known as bohr's theory.He argued that sub-atomic particles are not entirely governed by the laws of electrodynamics.He used quantum theory of energy.According to this theory energy cannot be lost or gained gradually(continuously) but discontinuously in the from of small packets or bundles called quanta.(singular quantum).The main postulates of bohr's model of atom are as follows:
1. In an atom,the electrons revolve around the nucleus in certain definite circular paths called orbits.
2. Each orbit is associated with definite energy and therefore,these are known as energy levels or shells.
3. As long as an electron remains in a particular orbit,it does not lose or gain energy even though it continues to revolve around the nucleus.
4.Only those orbits are permissible in which the angular momentum,(mvr)of the electron is a whole number multiple of h/2& i.e.Normally an electron continues to move in a particular energy level without losing energy.Such a state of an atom is called the ground state.
5.Energy is emitted or absorbed only when the electron jumps from one orbit to the other.
Success of bohr's model of atom:
1. It explains the stability of the atom.
2. It helps to calculate the energy of the electron in the nth orbit.
3. It explains successfully the line spectrum of hydrogen.
The following drawbacks are:
1.It fails to explain the spectra of multi-electron atoms i.e.,atoms containing more than one electron.
2.It fails to explain the cause of chemical combination and the shapes of the molecules arising out of it.
3.It fails to explain zeeman effect i.e.,splitting of spectral lines under the influence of arising out of it.
4.It fails to explain stark effect i.e.,splitting up of single line into a number of closely packed lines in  an electron field.
5.It fails to explain the three-dimensional model of an atom.
6.It fails to explain the relative intensities of spectral lines.
7.According to de-broglie,an electron has a dual character.
8.According to heisenberg's uncertainty principle,it is not possible to find the exact position and momentum of an electron.As such orbit cannot have a well-defined path as suggested by bohr. 
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