Vacuum tube experiments concluded that electrons, protons and neutrons are the fundamental particles of all atoms. Many hypothesis and experiments were proposed to know the distribution of these fundamental particles inside the atom. Thomson suggested a model of the spherical atom with positive charge distributed over the entire volume and electrons placed on it like plums on a cake. Rutherford tried to determine the structure of the atom experimentally.
Rutherford in 1911, carried out an experiment called ‘Gold foil experiment’ and could conclude the nature of an atom and the position of the protons present in the atom decisively. He also proposed the position and behaviour of electrons. They bombarded fragile sheets of gold foil with fast-moving alpha particles. Alpha particles, a type of natural radioactive particle, are positively charged particles with a mass about four times that of a hydrogen atom.
Observation of the experiment
Most of the alpha particles were indeed undeflected, a tiny percentage (about 1 in 8000 particles) bounced off the gold foil at extensive angles. Some were even redirected back toward the source.
Conclusion of the experiment
He concluded that all the positive charge and the majority of the mass of the atom must be concentrated in a minimal space in the atom’s interior, which he called the nucleus. The nucleus is the tiny, dense, central core of the atom and is composed of protons and neutrons.