Which of the following observations indicates that there is a small, dense, positively charged part in the center of an atom?

some uncharged particles are scattered by a gold foil.
all uncharged particles are attracted towards a gold foil.
all positively charged particles pass straight through a gold foil.
some positively charged particles bounce back from a gold foil.

Option D

Explanation:

Rutherford deduced that the atomic nucleus was positively charged because the alpha particles that he fired at the metal foils were positively charged, and like charges repel. Alpha particles consist of two protons and two neutrons, so they are positively charged. In Rutherford's experiments most of the alpha particles passed straight through the foil without being deflected. However, occasionally the alpha particles were deflected in their paths, and rarely the alpha particles were deflected backward at a 180 degree angle.

Since like charges repel, Rutherford concluded that the cause of the deflections of the positively charged alpha particles had to be something within the atom that was also positively charged. Rutherford concluded from his metal foil experiments that most of an atom is empty space with a tiny, dense, positively charged nucleus at the center that contains most of the mass of the atom.