Question

What might happen if sodium is kept in place of gold foil in the Alpha particle scattering experiment which is carried out by Rutherford?

Answer 1

The scattering angles would have changed, but the qualitative results would also change:
the reason Rutherford chose gold was that it is EXTREMELY malleable.
or any other One can stretch gold foil until it is only a few atoms thick in places, which is not possible with aluminum. If the foil were too thick, there would be no transmission of particles at all; the whole point was to demonstrate that most alpha particles passed through unchanged, but some of them scattered, which is only possible with a VERY thin foil.