(a) He selected a gold foil because he wanted as a thin layer as possible. This gold foil was about 1000 atoms thick.
(b) (i) As most of the alpha particles passed through undeviated, it means that they did not come across any obstruction in their part. Thus, most of the space in an atom is expected to be empty.
(ii) Very few particles deviated by small angles from their path which suggested that nucleus is positively charged.
(c) The revolution of the electron in any circular orbit is not expected to be stable. Any particle in a circular orbit would undergo acceleration.
During acceleration, charged particles would radiate energy. Thus, the revolving electrons would lose energy and finally fall into the nucleus. If this were so, the atom should be highly unstable and matter would not exist in the form that we know. We know that atoms are quite stable.