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Atoms

Question
CBSEENPH12039424

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

Solution

Bohr's postulate:

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.

Electrons revolve in a circular orbit. Centripetal force is provided by electrostatic force between electron and proton.

Given as,

mv2r = 14πr0e2r2

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, Thus

L = mvr = nh2π

3.

An electron may jump spontaneously from one orbit (energy level E1) to the other orbit (energy level E2) (E> E1); then the energy change AE in the electron jump is given by Planck’s equation

∆E = E2-E1 = hv

Where h = Planck’s constant.

And v = frequency of light emitted.

When the electron jumps from nth higher orbit to pth lower orbit it emits energy in form of the photon.

En - Ep = hv

According to de'Broglie hypothesis

λ = hp = hmv = 2πrnhmv = 2πrnh = 2πmvrL = nh2π