How did Rutherford interpret the following observations made during his \(\alpha\) -particle scattering experiments? (a) Most \(\alpha\) particles were not appreciably deflected as they passed through the gold foil. (b) A few \(\alpha\) particles were deflected at very large angles. (c) What differences would you expect if beryllium foil were used instead of gold foil in the \(\alpha\) -particle scattering experiment?

In Rutherford's scattering experiments, the fact that most α particles were not deflected as they passed through the gold foil led him to conclude that the atoms in the gold foil were mostly empty space. Since these positively charged α particles passed through without significant deviation, Rutherford concluded that the positively charged mass (protons) in an atom must be concentrated in a very small area at the center of the atom, called the nucleus. The electrons would then orbit around this small core of positive charge, occupying a majority of the atom's volume and leaving it largely empty.

The observation that a few α particles were deflected at very large angles indicated that there was a very strong repulsive force between the positively charged α particles and some part of the atom. This led Rutherford to conclude that the positive charge (and also most mass) in the atom was concentrated in a small, dense nucleus. When an α particle came close to this nucleus, the repulsive force between the two positively charged entities caused the deflection at large angles.

If beryllium foil were used instead of gold foil in the α-particle scattering experiment, we would expect some differences in the results: 1. The number of α particles that would be deflected at large angles would likely decrease. This is because beryllium has a lower atomic number (4) compared to gold (79) and thus has fewer protons and a less massive nucleus. As a result, the repulsive force experienced by the α particles as they approach the beryllium nuclei would be lower, making it less likely for the α particles to be deflected at large angles. 2. The overall scattering pattern might have a larger spread. Since beryllium atoms are lighter than gold atoms, the α particles would have a greater chance of transferring more of their kinetic energy to the beryllium nuclei during a collision. This could result in a larger spread of scattering angles for the α particles. 3. The thickness of the foil required for the experiment might need to be adjusted, as the lower atomic weight of beryllium could affect the stopping power of the foil, potentially allowing more α particles to pass through without significant deflection.