Question

In Rutherford's experiment, generally the thin foil of heavy atoms like gold, platinum etc. have been used to be bombarded by the α-particles. If the thin foil of light atoms like aluminium etc. is used, what difference would be observed from the above results?

Answer 1

Hint: We know that Rutherford performed the gold foil experiment, which made him conclude that the nucleus of the atom contains most of the atomic mass.

Complete step by step answer:
Rutherford Model of Atom:
Rutherford performed the gold foil experiment, which made him conclude that the nucleus of the atom contains most of the atomic mass. He observed that,
1.Majority of the $\alpha - $particles moved through the foil.
2.Few of the positively charged particles were deflected at very large angles.
3.Few of the particles were reflected back by ${180^o}$.

Conclusion of Rutherford’s Gold Foil experiment:
1.The nucleus of the atom contains most of the atomic mass.
2.The Atomic nucleus is entirely positively charged.
3.The atom consists of mostly empty space.
According to Rutherford model of atom,
An atom comprises positively charged particles and the mass of an atom is concentrated in a very small region called a nucleus. It was later discovered that nucleus consists of protons and neutrons.
The nucleus of an atom is surrounded by negative charged particles called as electrons and these electrons revolve around the nucleus in various discrete energy levels called as orbits.
The net charge on an atom is zero or electrically neutral because electrons are negatively charged particles and the nucleus is positively charged. The nucleus and electrons are held together by a strong electrostatic force of attractions.
The size of the nucleus is very small when compared to the total size of an atom.
Rutherford’s model of atom stated that the positive matter is concentrated in the central part of the atom called the nucleus. A nucleus of an atom is small, dense and heavy that contains protons (positive charge) and neutrons (no charge).
Heavy atoms like gold and platinum contain heavy nuclei. A large amount of positive charge is present in the heavy nucleus. When a beam of alpha particles are passed through the thin gold foil, several of them pass through without any deviations. However, some of the alpha particles deflected back (or) by small angles because of the enormous repulsive force present in the heavy nucleus. When a light aluminum is used, the number of alpha particles deflected back (or) those deflections that are caused by small angles would be negligible.
We have to know that a heavy nucleus contains a large number of positive charges and light nuclei contain a smaller number of positive charges. A larger repulsion is seen between alpha particles and heavy nuclei than repulsion between smaller nuclei and alpha particles. So, when aluminium foil is used the number of alpha particles would be more as the nucleus is smaller. A few numbers of alpha particles would be deflected because the number of positive charges present on lighter nuclei is less.

Note:
Now we discuss about the some of the drawbacks of Rutherford model as,
1.The stability of an atom could not be explained.
2.The revolution of electrons in the orbitals around the nucleus is not stable as the circling electrons in orbits would undergo acceleration and release energy.
3.This leads to energy loss and they would fall into the nucleus.