Question

Sketch Rutherford's atomic model. Why is Rutherford's model of the atom called the planetary model?

Answer 1

Hint: In this question we have been asked to sketch Rutherford's atomic model. We have also been asked to clarify as to why Rutherford’s atomic model is called the planetary model. Therefore, to answer this question we shall discuss Rutherford's atomic model. We shall also discuss the famous gold foil experiment by Rutherford that helped him obtain the atomic model.

Complete answer:
After the discovery of atoms by John Dalton and electrons by J.J Thompson, Rutherford discovered the nucleus of atoms. Dalton proposed that atoms were indivisible. However, he was proven wrong after the discovery of the first subatomic particle i.e. the electron. J.J Thompson in his theory proposed that an atom is like a plum pudding, where the negatively charged electrons are scattered in the field of positive charge.
                           

In 1911 Ernest Rutherford carried out an experiment through which he confirmed that an atom is made of a massive region of positive charge at the centre and electrons revolving around this positive charge. In his experiment of gold foil, Rutherford bombarded the alpha particles on a very thin sheet of gold foil. Surrounding this foil, he placed a photosensitive screen that would light up as the when the alpha particles struck it. When he saw the results, he observed that all the positive charge was concentrated at the centre of the nucleus as shown in above diagram. The experiment showed that the rest of the atom is empty space except for electrons which revolve around the nucleus. Rutherford’s model of atoms represented the solar system. Where the positive charge is at the centre like the sun and electrons revolve around it like a planet.
Therefore, his model is known as planetary model.

Note:
Rutherford also predicted the presence of the neutral particles known as neutrons. However, he was unable to find the neutrons through experiments. Several years later, the neutrons were discovered by his student James Chadwick. Even though new models of atoms have been put forward by other scientists such as Niels Bohr, Rutherford's atomic model is still used on primary level to explain the structure of atoms. It is however not very popular with higher level education.