Bohr's Atomic Model

 In this theory, atomic model of Bohr is explained here.

Bohr’s Atomic Model

The atomic model is proposed by Bohr in 1913. The Bohr has made following assumptions.

  • The atom has massive positive charged nucleus. 
  • The electrons revolve round their nucleus in circular orbits. 
  • The centrifugal force between electron and nucleus is balanced by electrostatic pull. 
  • The electron cannot revolve round the nucleus in any arbitrary orbit but certain definite discrete orbits (stationary orbits). 
  • The orbital angular momentum of the electron is equal to an integral multiple of h/2π
  • Orbital angular momentum = nh / 2π
  • Where n = Integer,    h = Planck’s constant
  • The electrons do not radiate out any electromagnetic energy while revolving in the stationary orbits. In other words. the orbits are non-radiating path of the electron.

Frequency of Emitted Photons

  • When electrons jump from one orbit to another orbit, the atom radiates out energy. 
  • If E1 and E2 are the energy of the two orbits before and after electron jump, the frequency of the emitted photon is given by

       E1 – E2 = hf

       ΔE = hf

       Where f = Frequency of the emitted radiations

  • If I is moment of inertia of an electron and ω is its angular velocity, then

       ωI = nh / 2π

      ( mr2 ) ω = nh / 2π

      ( mr2 ) ( v / r ) = nh / 2π

      mvr = nh /  2π

  • The n is called as principal quantum number or Bohr’s circular orbit and it is first, second and third orbits etc…. If fixes the size of allowed orbits

                = 1, 2, 3 etc

  • momentum of revolving electron = mv
  • moment of electron about nucleus = mvr


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