What evidence supports the nuclear model of the atom?

The nuclear model of the atom is supported by evidence from Rutherford's gold foil experiment and alpha particle scattering.

Ernest Rutherford's gold foil experiment in 1909 provided the first significant evidence for the nuclear model of the atom. In this experiment, Rutherford and his team fired alpha particles (helium nuclei) at a thin sheet of gold foil. They expected the particles to pass straight through the foil, based on the then-accepted 'plum pudding' model of the atom. However, they observed that some particles were deflected at large angles, and some even bounced back. This could only be explained if the majority of the atom's mass and positive charge were concentrated in a small central nucleus, with the electrons orbiting around it. This led to the proposal of the nuclear model of the atom.

Further evidence for the nuclear model came from alpha particle scattering experiments. These experiments involved firing alpha particles at various substances and observing how they were deflected. The results showed that the deflections could only be explained if the positive charge and most of the mass of the atom were concentrated in a small central nucleus. This supported Rutherford's nuclear model of the atom.

In addition, the discovery of the neutron in 1932 by James Chadwick provided further support for the nuclear model. Neutrons, along with protons, make up the nucleus of an atom. The discovery of the neutron helped to explain why atoms have mass and how different isotopes of the same element can exist.

Finally, the development of quantum mechanics in the early 20th century also supported the nuclear model. Quantum mechanics describes how electrons move in 'orbitals' around the nucleus, rather than in simple circular orbits as initially proposed by Rutherford. This more sophisticated model of electron behaviour fits well with the nuclear model of the atom.