Rutherford's model of an atom and alpha particle scattering experiment

This is the presentation of Rutherford model of an atom.

1. RUTHERFORD’S MODEL OF AN ATOM AND ALPHA PARTICLE SCATTERING EXPERIMENT

2. CLASS 9 th LOTUS PREPARED BY:-HARSH RAJPUT

3. ACKNOWLEDGEMENT I would like to thank my science teacher Shalini Mam and my parents for helping me in making this presentation. M y parents helped me in editing of this presentation. They also helped me in formatting the matter of the presentation. I collected the information from the internet and from some books.My other gratitude I would like to convey to my school who suggest me to make this and to have marks for adding it into examination.

4. Ernest Rutherford (1871-1937) Ernest Rutherford, first known as Baron Rutherford  (30 August 1871 - 19 October 1937) was a New Zealand-born British chemist and physicist who became known as the father of nuclear physics. He is considered the greatest experimentalist since Michael Faraday (1791–1867). In early work he discovered the concept of radioactive half-life, proved that radioactivity involved the transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation.  

5. This work was done at McGill university in Canada. It is the basis for the Nobel Prize in Chemistry he was awarded in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances ” . Structure of an Atom

6. ABOUT THE EXPERIMENT Rutherford scattering experiment   is a phenomenon in  physics  that was explained by  Ernest Rutherford  in 1911 , which led to the development of the  Rutherford model  (planetary model) of the  atom , and eventually to the  Bohr Model . It is now exploited by the materials  analytical technique Rutherford Backscattering . Rutherford scattering is also sometimes referred to as Coulomb scattering because it relies only upon  static electric  ( Coulomb ) f orces , and the minimal distance between particles is set only by this potential. The classical Rutherford scattering of alpha particles against gold nuclei is an example of "elastic scattering" because the energy and velocity of the outgoing scattered particle is the same as that with which it began.

7. Rutherford also later analyzed inelastic scattering when he projected alpha particles against hydrogen nuclei (protons) ; however this latter process is not referred to as "Rutherford scattering", although Rutherford was first to observe it. At the end of such processes, non-coulomb ic forces come into play. These forces, and also energy gained from the scattering particle by the lighter target, change the scattering results in fundamental ways which suggest structural information about the target. A similar process probed the insides of nuclei in the 1960s, and is called deep inelastic scattering .

8. Apparatus Gold Foil Lead Block Shield Zinc Sulphide Screen Source of Alpha particles

9. A narrow beam of alpha particles was aimed at a thin sheet of gold foil . A zinc sulfide coated screen surrounding the gold foil produced a flash of light when struck by an alpha particle (radioactive materials expose photographic film) . By noting where the flashes occurred, the scientists could determine if the atoms in the gold foil deflected the alpha particles . PROCEDURE

10. OBSERVATION Most of the particles went straight through the gold foil Several particles were deflected straight back toward the source! A few particles were deflected at large angles.

11. Interpreting the Observed Deflections * * * * * * * * * * * * * * gold foil D eflected particle U ndeflected particles * * B eam of alpha particles *

12. C O N C L U S I O N As a result of his observations, Rutherford suggested that the atom had a positively charged centre which contained most of the mass. h e called the heavy positively charged centre the nucleus. h e went on to suggest that the nucleus was surrounded by orbiting electrons required for electrical neutrality.

13. DRAWBACKS The major drawback of Rutherford’s model of an atom is that it does not explain the stability of the atom. In the Rutherford’s model of an atom, the negatively charged electrons are revolving around the positively charged nucleus in circular paths. Now, we know that if an object moves in a circular path, then its motion is said to be accelerated. This means that the motion of an electron revolving around the nucleus is accelerated.

14. If we apply this electromagnetic theory to the Rutherford’s model of an atom, it will mean that the negatively charged electrons revolving around the nucleus with accelerated motion , will lose their energy continuously by radiation. Thus, the energy of revolving electrons will decrease gradually According to the electromagnetic theory of physics, if a charged particle undergoes accelerated motion, then it must radiate energy (or lose energy) continuously. and their speed will also go on decreasing. The electrons will then be attracted more strongly by the oppositely charged nucleus due to which they will come more and more close to the nucleus. And ultimately the electrons should fall into the nucleus by taking a spiral path. This should make the atom very unstable and hence the atom should collapse.

15. T H A N K Y O U