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What is Atomic physics ? Atomic physics notes, pdf, formulas etc.

-: ATOM MODEL

Man had always been curious to know the details of the constituent of matter. Structure of atom, which is the smallest particle of matter which takes part in a chemical reaction, has always been one of the main targets of scientists.
        An explanation regarding the structure of atom is called an atom model .

-: THOMSON'S ATOM MODEL

J. J.  Thomson gave the first idea regarding structure of atom. The model is known after him as Thomson's atom model . According to this atom model whole of the positive charge is distributed uniformly in the form of a sphere. Negatively charged electrons are arranged with in this sphere here .πŸ‘‡πŸ‘‡
The model is popularly known as plum-pudding model . Every electron is attracted towards the centre of uniformly charged sphere while they exert a force of repulsion upon each other.

-: RUTHERFORD'S EXPERIMENT

Rutherford performed experiments on the scattering of alpha* particles by extremely thin metal foils.
                  A radioactive source (radon) of alpha-particles was placed in a lead box having a narrow opening. πŸ‘‡πŸ‘‡
This source emits alpha-particles in all possible directions. However, only a narrow beam of alpha particles emerged from the lead box, the rest being absorbed by the lead box. This beam of alpha-particles is made incident on a gold foil whose thickness is only one micron, i.e., 10^-6 m. When passing through the metal foil, the alpha-particles get scattered through different angles. These particles fall on a fluorescent screen, producing a tiny flash of light on the screen. This can be easily viewed by a low power microscope in a dark room.
           In 1913, Geiger and Marsden performed a more sensitive experiment on the scattering of alpha-particles on the guidelines suggested by Rutherford. Like here πŸ‘‡
Apparatus consists of an air tight chamber 'C' which can be evacuated by a tube 'T' (fig.18.3πŸ‘†). The chamber is capable of rotation inside a jacket 'R' about a vertical axis. The source 'S' of alpha-particles, radon, is placed inside a lead cavity 'L' . alpha-particles, after coming out of the narrow opening in the lead cavity, strike a thin foil 'F' . This foil is made of some metal of high atomic weight like gold, silver or platinum. The foil is placed at the centre of chamber 'C' . Scattered alpha-particles are viewed through low power microscope 'M', which is provided with a fluorescent screen.

-: RUTHERFORD'S ATOM MODEL

On the basis of the conclusions drawn from Rutherford's experiment, a new atom model was proposed. This atom model, known as Rutherford's atom model , has following characteristics:

(i) An atom consists of equal amounts of positive and negative charge so that atom, ad a whole, is electrically neutral.
(ii) The whole of positive charge of the atom and practically whole of its mass is concentrated in a small region which forms the core of the atom, called the nucleus.
(iii) The negative charge, which is contained in the atom of electrons, is distributed all around the nucleus, but separated from it.


-: BOHR'S ATOM MODEL

Following some serious objections to Rutherford's atom model, Bohr suggested some modifications in the atom model. The modified atom model is called Bohr's atom model whose basic postulates are described below :
(i) The central part of the atom called nucleus , contains whole of positive charge and almost whole of the mass of atom. Electrons revolve round the nucleus in fixed circular orbits.
(ii) Electrons are capable of revolving only in certain fixed orbits, called stationary orbits or permitted orbits . In such orbits they do not radiate any energy.
(iii) When revolving in permitted orbit an electron possesses angular momentum 'L' (=mvr) which is an integral multiple of h/2Ο€
i.e.,.                      
                               L = n . h/2Ο€
Where 'n' is an integral and 'h' is Plank's constant.
(iv) Electrons are capable of charging the orbits. On absorbing energy they move to a higher orbit while emission of energy takes place when electrons move to a lower orbit. If 'f' is the frequency of radiant energy,
                                  hf = W2 -W1
Here. W1 = energy of electron in lower orbit.
           W2 = energy of electron in higher orbit
(v) All the laws of mechanics can be applied to electron revolving in a stable orbit while they are not applicable to an electron in transition.

-: BOHR'S THEORY OF ATOMIC STRUCTURE

  To completely view of Bohr's atomic model check below on referred pdf note of Bohr's atomic model.

Click here πŸ‘‡πŸ‘‡

https://drive.google.com/file/d/1011iUI1OtSq5Gqajgc_4Vqsq8KyQPRug/view?usp=drivesdk


-: HYDROGEN SPECTRUM

As transition of electron takes place from a higher orbit to a lower orbit, difference of energy is radiated in the form of radiation. The wavelength of the radiation depends upon the initial and final orbit within which the transition takes place. Accordingly a number of series are emitted. Each series is composed of a number of lines. Like here πŸ‘‡πŸ‘‡

To completely study about Atomic physics like:   photoelectric effect, failure of Rutherford's atomic model, Bohr's theory of atomic structure, . To these notes Click here πŸ‘‡πŸ‘‡

https://drive.google.com/file/d/1-nsKj51xL-jznnUJuhpiahNf5E-R0mPq/view?usp=drivesdk


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