CBSE Class 11-science Answered

To increase the probability of an alpha particle hitting a nucleus, the more you have in a given volume, the better you chances. Gold has a density of 19.3 grams per cubic centimeter. Gold is capable of being rolled to extremely thin foils (it's one of the most malleable metals), so the beam of alphas will not be totally absorbed. There are elements with higher density than gold: Osmium, Iridium and Platinum. But, Os, Ir, and Pt are much rarer elements than gold, much more expensive, and not easily rolled to a very
thin foil necessary for the Rutherford experiments. Hence, gold foil was used for the Rutherford's experiment.