Rutherford Bombarded Gold Foil with Alpha (A) Particles and Found

Multiple Choice

Rutherford bombarded gold foil with alpha (a) particles and found that a small percentage of the particles were deflected. Which of the following was not accounted for by the model he proposed for the structure of atoms?

A) the small size of the nucleus
B) the charge on the nucleus
C) the total mass of the atom
D) the existence of protons
E) the presence of electrons outside the nucleus