Question

What is a gold-foil experiment?

Answer 1

This gold-foil experiment was done by Physicist - Ernest Rutherford. He was born in New-Zealand. This experiment was done in order to find out the structure of an atom. Other than gold-foil experiment, this experiment has various other names such as: planetary model of the atom or nuclear atom.

Complete answer:
This experiment was done by Ernest Rutherford after an experiment called plum-pudding model which was done by J.J Thomson.
This experiment was done by using a thin sheet of golf foil, a radioactive source emitting alpha particles and a fluorescent screen which surrounds the gold sheet. He placed the radioactive source in front of the gold sheet and it was surrounded by a fluorescent screen. Now, this gold foil sheet was bombarded with the alpha particle from that radioactive source.
From this experiment, certain observations were made such as:
A huge amount of $\alpha$-particles was able to pass through the gold foil without experiencing any kind of deflection which indicated that a large amount of space is unoccupied in an atom.
Some amount of $\alpha$-particles experienced deflection by very small angles. This indicates that positive charged particles are present in an atom but in a very confined space.
A very few amount of $\alpha$-particles experienced deflection by an angle of $180^\circ$which indicated that positively charged species are present in an atom in a very small amount as compared to the total volume of the atom.
Therefore, on the basis of the above observations, the atomic structure was discovered by Rutherford. And then he gave his model, called Rutherford atomic model.
As per the model:
The region in which the positively charged species are present in an atom is known as nucleus.
In a circular manner, the electrons revolve around the region where the positively charged species are present, that is, nucleus. And the circular path is known as an orbit.
The electrons, that is, the negatively charged species and the positively charged species are present in a very small space, so they are bonded together with a force called electrostatic force of attraction.
Hence, the structure of an atom was discovered by Rutherford.

Note:
This model has certain limitations as well, such as: this model does not talk about the stability of an atom, this model failed to explain that if the electrons are revolving around the nucleus in a circular manner then the electrons will gain energy and therefore the structure will collapse and since it does not happen, this model was not able to explain the reason behind it.