In Rutherford’s experiment, generally the thin foil of heavy atoms like gold, platinum etc. have been used to be bombarded by the α-particles. If the thin foil of light atoms like aluminium etc. is used, what difference would be observed from the above results?

Heavy atoms (like gold and platinum) have a heavy nucleus carrying the huge amount of positive charge. As a result of bombardment, some α-particles are easily deflected back on hitting the nucleus. Also, a number of α-particles are deflected through small angles because of large positive charge on the nucleus. If we use light atoms such as aluminium, then such atoms will be light and have a small positive charge on the nucleus. Hence, the number of particles deflected back and those deflected through the same angle will be negligible.