Rutherford model atom

Rutherford model of an atom

Around the year 1911, A British physicist Ernst Rutherford carried out the famous gold foil experiment.

He did this to understand structure of the atom the experiment was carried out by Rutherford along with Hans Geiger and Ernest Marsden.  The experiment he performed  was the breakthrough in the  field of chemistry. Which helped him to understand structure of atom in more accurate manner .

Experiment:

  • Sorce alpha particle or He2+ particles used locked in alead container with very small slit. Thus ensure that the alpha particle only came out through the small opening. And travel in a straight line .
  • Why he choose alpha particle? Because alpha particle were having high energy and heavier as well, so if atom is pudding positive charge particle in it then the alpha particle pass through by them because they are heavier.
  • The greater mass and energy compared to protons. Made him choose alpha particle for the experiment.
  • Next he used Gold foil on which the alpha particle would bombarded.
  • Why did he choose a gold foil? Because a very thin layer was required for this experiment. This gold foil was estimated to contain 1000 atoms.
  • Lastly we able to locate the circular band with a gap this is screen a fluorescent screen, that would help to detect radiation.
  • That means the screen will glow or emitted fluorescent light whenever alpha particle will hit it.
  • So this has the traced of alpha particle by the deflection screen.

Observation:

  • The alpha particle were emitted from the lead box (He2+) this directly hit the gold foil from small opening slit.
  • By idea of Thomson’s model, Rutherford expected the alpha particle pass right through the gold foil and hit in straight lines to the deflection screen or detector.
  • Because the mass of alpha particle is heavier than the mass of positive charges , that mean it should be direct hit the gold foil and move ahead through it.
  • But he was astonished to get the results!

He found the following observation.

i) Most of the fast moving alpha particle passed straight through the hold foil.

ii) Some of the alpha particle deflected by the foil by small angel.

iii) Surprisingly one out of every 12000 particles appear to be rebound.

  • In the word of Rutherford “this results was almost as incredible as you fire a 15 inch shell at a piece of tissue paper and it come back and hit you.

Hypothesis by Rutherford:

  • Three observation made Rutherford to really think thatThomson’s model is not really correct, based on conclusion he move forward and explain the structure of atom.
  • There is positive charge centre in an atom called nucleus. Nearly all the mass of the atom reside in the nucleus.
  • The size of the nucleus is very small as compared to atom
  • The electrons revolve around the nucleus in circular path. So that Electrons outside the nucleus atom almost entirely empty space.
  • The Necessary centripetal force provided electrostatic attraction between nucleus and the electrons.
  • He gave no further justification for the assumption.

Drawbacks of Rutherford model:

  • Rutherford model of an atom doesn’t explain the stability of atom. According to the electromagnetic theory During the acceleration, charged particles loss energy , this lose of energy slow  down the electron and eventually the electron fall into the nucleus and the atom collapse.
  • Rutherford atom of model doesn’t describe anything about the distribution of electron and energies of the electrons.
  • Rutherford model of an atom was unable to explain the line spectra given by every element.

 

Question answer:

1) Why did he choose only alpha particle?

Answer: Rutherford choose only alpha particle because alpha particle were having high energy and heavier as well, so if atom is pudding positive charge particle in it then the alpha particle pass through by them because they are heavier.

2) Why did he choose only Gold foil?

Answer: He choose only Gold foil because a very thin layer was required for this experiment. This gold foil was estimated to contain 1000 atoms.

3) Why Rutherford expected alpha particle pass through gold foil?

Answer: Rutherford expected the alpha particle pass right through the gold foil and hit in straight lines to the deflection screen or detector.

Because the mass of alpha particle is heavier than the mass of positive charges , that mean it should be direct hit the gold foil and move ahead through it.

4) What Rutherford found after observation?

Answer: Rutherford found after observation are following.

  • Most of the fast moving alpha particle passed straight through the hold foil.
  • Some of the alpha particle deflected by the foil by small angel.
  • Surprisingly one out of every 12000 particles appear to be rebound.

5) What are the drawbacks of Rutherford model of atom?

Answer:   Rutherford model of an atom doesn’t explain the stability of atom. According to the electromagnetic theory During the acceleration, charged particles loss energy  , this lose of energy slow  down the electron and eventually the electron fall into the nucleus and the atom collapse.

  • Rutherford atom of model doesn’t describe anything about the distribution of electron and energies of the electrons.
  • Rutherford model of an atom was unable to explain the line spectra given by every element.

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