Rutherford 's Gold Foil's Experiment: Rutherford's experiment on scattering of alpha particles

 The ancient Greeks first Proposed the word "Atom" as the name for an indivisible unit of matter.

Rutherford's several experiments have led to an understanding of the structure of atoms. There are some famous experiments such as experiments of Rutherford's atomic model, and Rutherford's gold foil experiment.

What is Atom?

The matter is composed of the smallest, individual particles known as atoms.

What is Radioactivity?

The process of disintegration of the nuclei of unstable atoms results in loss of energy in the form of radiations such as alpha, beta, and gamma is called radioactivity.

Rutherford's Experiment for Radioactivity:- 

In 1902 Rutherford devised an ingenious method for the separation of rays from each other. To perform the experiment, he used two plates that contains positive and negative charges. He passed rays through these plates. He placed a lead block as a sample of a radioactive substance in between two plates of a magnet then he set a photographic plate on top of the lead block. During the performance of experiments, the radiations begin to resolve into three components

Observation of Rutherford:-

He gave his observation that these rays which are emitting from the radioactive substance are of three types then he further explained those rays which are moving towards -ve plate are known as alpha rays. While those rays are deflected towards the +ve plate which is called beta rays. Those rays did not move anywhere which means it carries no charge and is called gamma rays. To make your understanding I.W.N present a diagram:

There are some properties to understand the nature of these rays:

properties of radioactive rays:-

Properties of Alpha Rays:-

1)     1)These rays contain positive charge particles.

2)    2) These particles are fast-moving helium nuclei which mean consist of two protons and two neutrons.

3)    3) The velocity of particles is approximately the same as the one-tenth velocity of light.

4)  4)   They have low penetrating power but their ionization power is high.

5)    5) They ionize the air.

Properties of Beta Rays:-

1)    1) The beta rays have negatively charged particles.

2)   2)  These particles are fast-moving electrons.

3)   3)  The velocity of beta particles is equal to the velocity of the light approximately.

4)  4)   They have much greater penetration power as compared to alpha rays.

5)   5)  These rays ionize gases to less extent. 

Properties of Gamma Rays:

1)Gamma rays do not consist of particles. These are electromagnetic radiations.

2)They do not carry any charge so they neither deflect towards the positive plate nor the negative plate.

3)Their velocity is equal to the speed of light.

4)They have great power of penetration because of their high speed and non-material nature.

Rutherford’s Gold foil Experiment:-

As we know an atom consists of a proton and electron that revolves around it. Rutherford and Marsden performed their historic experiment “Alpha particle scattering experiment” in 1909. To further insist on the interior of the atom. He used a radioactive source to burn alpha particles. Then he took a thin sheet of gold foil with a thickness of 0.004 cm. He placed a screen that surrounds the alpha particles, in this way, he noted the strike of alpha particles. He also observed that most of the alpha particles passed straight through the gold foil and thus producing a flash on the screen behind the screen. This showed that the gold atoms deflected or scattered alpha particles at large angles So that some of them bounced back.

Conclusion of Rutherford's Gold Foil Experiment:-

After the experiment was concluded, Rutherford was surprised at the result. Although most of the alpha particles passed through the gold foil as he expected. While some of them reverse back at extreme angles. Rutherford was confused then he placed a cannonball at a tissue piece and begin to observe the bounce back of particles. These results led him to indicate that the gold atom had a structure of a positive region inside it. But protons were not yet discovered because protons were present in a very tiny portion of a nucleus as shown in the above diagram. You can also see in label A of the diagram most alpha particles are passing through the gold foil without any deflection. While some of them are bouncing back at large angles like the other labeled B in the above diagram. One thing was found that these particles should be passed to the positive portion to be bounced back. The most interesting results were those same to label C in the above diagram. After a deep observation, Rutherford finally concluded that the atom consists of empty spaces, that allow the passing of the majority of particles through gold atoms without any interference. He also explained that traces of deflected rays are proof of a positive portion in the center of the nucleus. These were the result that promoted him to propose some  Postulates of the Atomic Model which are discussed below:

Postulates of Rutherford's Atomic Model:-

1)Major portion of the atom is empty.

2)Atom has a positively charged center known as the nucleus.

3) Nucleus contains most of the mass of an atom is concentrated in tiny portion.