JOURNEY INSIDE THE ATOM-2

PRERNA FOR IAS

         Mehnat Aapki, Guidance Humari

         Roz ki Prelims Practice — Experts ke Saath

JOURNEY INSIDE THE ATOM-2

1. Difference Between Thomson's Model and Rutherford's Model

Thomson's and Rutherford's atomic models differ significantly in explaining atomic structure. Thomson proposed that the atom is a positively charged sphere with electrons embedded throughout, like plums in a pudding. He believed positive charge was spread uniformly and there was no nucleus. Rutherford, based on the gold foil experiment, suggested that the atom has a tiny, dense, positively charged nucleus at the centre containing most of its mass. Electrons revolve around this nucleus, and most of the atom is empty space. Rutherford's model successfully explained alpha-particle scattering, whereas Thomson's model failed to account for these observations.

2. Discovery of the Proton

The proton was discovered by Ernest Rutherford in 1919 during experiments involving the bombardment of nitrogen gas with alpha particles. He observed that positively charged hydrogen nuclei were emitted and concluded they were fundamental particles present in all atomic nuclei. These particles were named protons. The discovery established that the nucleus carries a positive charge and contains protons. It also helped explain atomic number and the identity of elements. Along with electrons and later-discovered neutrons, protons became one of the three fundamental subatomic particles, playing a crucial role in understanding atomic structure and nuclear science.

3. Discovery of the Neutron

The neutron was discovered by James Chadwick in 1932. While bombarding beryllium with alpha particles, Chadwick observed a highly penetrating radiation that had no electric charge. He concluded that this radiation consisted of neutral particles with a mass nearly equal to that of protons, which he named neutrons. The discovery solved the mystery of why atomic masses were greater than the number of protons alone. Neutrons contribute to the stability of the nucleus and help explain isotopes of elements. Their discovery completed the understanding of the three major subatomic particles in an atom.

4. Evolution of Atomic Models