Rutherford’s alpha-particle scattering experiment, conducted in 1909, played a pivotal role in understanding the structure of the atom. Here’s an explanation:

Rutherford’s Experiment:
– Rutherford and his team aimed alpha particles (positively charged particles) at a thin gold foil.
– They expected that according to Thomson’s “plum pudding” model, the alpha particles would pass through the gold foil with minimal deflection or deviation.

Observations:
– Most alpha particles did pass through the foil without any deviation.
– However, a small fraction of alpha particles (about 1 in 8000) were deflected at large angles, and some even bounced straight back.

Interpretation:
– The unexpected deflections and some particles bouncing back directly contradicted Thomson’s model.
– Rutherford’s interpretation was groundbreaking: He proposed that atoms had a dense, positively charged central core called the nucleus.

Discovery of the Atomic Nucleus:
– Rutherford concluded that most of the atom was empty space because most alpha particles passed through undeflected.
– However, the few instances of large deflections and some particles bouncing back suggested encounters with a highly concentrated, positively charged nucleus, deflecting the positively charged alpha particles.

Significance:
– The discovery of the atomic nucleus overturned the prevailing Thomson model, suggesting that the atom was not a homogeneous, positively charged sphere but had a small, dense, and positively charged nucleus at its center.
– This experiment laid the foundation for the nuclear model of the atom, with a nucleus containing protons and later the discovery of neutrons.

In summary, Rutherford’s experiment led to a fundamental shift in our understanding of atomic structure by revealing the existence of a dense, positively charged atomic nucleus, marking a significant milestone in the development of atomic theory.