Bohr’s Model of Atom
- The central part of an atom is called the nucleus.
- Electrons revolve around the nucleus and have fixed energy levels called shells or orbits.
n=1 K
n=2 L
n=3 M
- An electron can move only in those orbits for which the angular momentum is an integral multiple of h/2π
h= Planck constant
- While moving in a particular shell on an electron neither absorbs nor loses energy.
- By absorbing energy an electron can jump from one orbit to another orbit. The difference in the energy is given by ∆E= hv
To overcome the defects of the Bohr model of the atom there are two concepts:
Dual Behaviour of Matter
De-Broglie suggested that small particles have also the property of a wave.
De-Broglie equation : λ = h/mv
where,
λ= wavelength
h= Planck’s constant
m= mass of a particle
v= velocity of the particle
Big particles like moving stone ball etc. do not show the property of a wave because their mass is high hence the wavelength is too short to measure.
Heisenberg Uncertainty Principle
It is impossible to measure simultaneously the position and momentum or velocity of a small moving particle with absolute accuracy.
∆p. ∆x = h/4π
Or
m.∆v. ∆x = h/4π
Where,
∆p= uncertainty in the momentum
∆x= uncertainty in the position of the particle
∆v= uncertainty in the velocity
m= mass of the particle.
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