Why did the alpha particles bounce back during rutherford's experiments? they hit other alpha particles. they hit electrons. they hit positive charges in the gold atoms. they hit the collector film.

They hit positive charges in the gold atoms.
As alpha particles are positively charged particles, they will experience repulsion force as soon as they approach positive charges in the center of the atom (in the nucleus).
Also remember that back at Rutherford time, they did not have the right visualization of the atom, they had a model of it like if it was a budding of positive charges and the negative charges are put into them. So this experiment gave a really better and more reliable imagination of the atom structure.

Hope this helps.