CHAPTER 5
(ATOMIC MODEL)
Frank-Hertz Experiment
The Rutherford Model
Bohr’s Model of Hydrogen-Like Atom 
emit and absorb EM radiation 
Plum Pudding Model 
microscopic size 10^10 m
electrically neutral
stable
atom is embedded in a cloud of positive charges that exactly neutralize that of the electrons.
the electrons sit at their respective equilibrium position
attraction of the positive cloud balance mutual repulsion
How to interpret the Rutherford scattering experiment?
a very small but massive kernel inside the atom.
diffused distribution of the positive charge
Infrared catastrophe: insufficiency of the Rutherford model
has a fatal flaw: it predicts the collapse of the atom within 10^10s
An accelerated electron will radiate EM radiation
orbiting electron to loss energy and consequently spiral inward and impact on the nucleus
.
The nucleus is surrounded by only a single electron.
assume the centre of the circular motion of the electron coincides with the centre of the nucleus.
We term such type of simple system: hydrogen-like atoms.
hydrogen atom corresponds to Z = 1
Postulate
- Mechanical stability (classical mechanics)
- condition for Orbit stability
- Quantization of velocity and radius
- Quantization of energy level
excitation of atoms to discrete energy levels
consistent with the results suggested by line spectra.
Mercury vapour is bombarded with electron accelerated under the potential V
Balmer series and the empirical emission spectrum equation
Experimental
RH = 1.0973732 x 10^7 m-1
Theoretical
