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Question:

State Bohr's postulate to define stable orbits in hydrogen atom. How does de Broglie's hypothesis explain the stability of these orbits?

Solution:

A) Bohr's Postulates

  1. An atom has a number of stable orbits in which an electron can reside without the emission of radiant energy. Each orbit corresponds, to a certain energy level.
  2. An electron may jump spontaneously from one orbit (energy level E1) to the other orbit (energy level E2) (E2>E1); then the energy change ΔE in the electron jump is given by Planck's equation ΔE=E2−E1=hv
  3. The motion of an electron in a circular orbit is restricted in such a manner that its angular momentum is an integral multiple of h/2π
  4. A special surface around the nucleus which contained orbits of equal energy and radius was called the shell. These shells are numbered from inside to outwards as 1, 2, 3, 4 etc. and called K, L, M, N respectively.
    B. λ=RH[1/1²] λ=1615RH
    Frequency=c/λ =2.8×10¹⁵Hz