Why do electrons not reflect alpha particles?

Atomic structure

The animation in Fig. 8 shows the modern (atomic nucleus made up of positively charged protons and electrically neutral neutrons) explanation of the scattering experiment by GEIGER and MARSDEN: Those alpha particles that penetrate the foil far enough from nuclei are hardly deflected. Only the few projectiles that fly very close to a core experience a significant deflection. The following applies: The smaller the distance to the core, the greater the scattering angle.

Overall, RUTHERFORD's atomic model with the atomic nucleus explains the three main results of the GEIGER and MARSDEN experiment:

1. The nucleus is so small that the overwhelming majority of all alpha particles move through the gold foil without any deflection, as if there were nothing there. It looks like the atom is mostly empty space. The interaction of the charged alpha particles with the shell electrons does not lead to any significant deflection due to the relatively high kinetic energy of the alpha particles and the much larger mass compared to the electrons.

2. Only a few alpha particles come so close to an atomic nucleus when passing through the foil that the electrical repulsion of the two positively charged corpuscles leads to a slight deflection of the alpha particle by one or two degrees. The probability of this proximity to the core and the resulting distraction were calculated by RUTHERFORD and his colleagues and compared with the test results. There was a very good match.

3. Only very few alpha particles hit the center of the atom almost directly. The alpha particles, which approach the atomic nucleus at around 10% of the speed of light, are "reflected" in a fully elastic manner by its electrical forces. Since the alpha particle is much lighter than the gold core, it is "reflected" on a hyperbolic path, so that it is deflected by an angle of 90 ° and more. During this collision, the core absorbs only a small amount of energy from the alpha particles, but this is insufficient to detach the atom from the metal compound.