Question

why did a few of the alpha particles rebound ?

Answer 1

" Only a few particles bounced back because the nucleus is so small / atom is mostly empty space that few collided with a nucleus . If they bounced back it was because of alpha particle and nucleus are positive : repulsion if they bounced back it was because nucleus is massive / dense so alpha particles rebound . "

Answer 2

Few alpha particles rebound because they are very light and they can stop by thin aluminum sheet and human skin and there is very less biological damage .when it is reflected to thing gold wire then then all passes through it but some who directly hits to the middle of gold wire reflects and rebounds proved by Rutherford's experiment