Alpha particle scattering experiment

In physics and the other sciences, theories develop through the collection of experimental data. In this section we explore how the alpha particle scattering experiment provided the data for the nuclear model of the atom.

Rutherford’s Alpha Scattering Experiment

Rutherford’s alpha scattering experiment was a groundbreaking study that disproved the "plum pudding model" and supported the nuclear model of the atom.

The Experiment:

• Alpha particles (positively charged) were directed at a thin sheet of gold foil.

• The scattering of these particles was carefully observed.

Key Observations and Conclusions:

1. Atoms are Mostly Empty Space:

   • Most alpha particles passed through the gold foil without deflection.

   • This showed that atoms are primarily empty space.

2. Small, Dense Nucleus:

   • A small fraction of alpha particles were deflected at large angles.

   • This indicated the presence of a dense region (the nucleus) at the center of the atom.

3. Positively Charged Nucleus:

   • Some alpha particles were repelled and deflected at shallow angles, confirming that the nucleus has a positive charge.

Overhead view of the alpha particle scattering experiment

Impact on Atomic Theory

The alpha particle scattering experiment:

• Rejected the Plum Pudding Model: This model proposed that electrons were embedded within a diffuse positive substance.

• Introduced the Nuclear Model:

  • A tiny, dense, positively charged nucleus is at the center of the atom.

  • Electrons orbit the nucleus, much like planets orbit the sun.

The plum pudding and nuclear models of the atom