What conclusion did Rutherford draw from his gold-foil experiment? A. Almost all the mass of an atom is concentrated in the nucleus. B. Atoms contain three different subatomic particles. C. Electrons are tiny particles that carry a negative charge. D. The mass of a proton is nearly equal to the mass of a neutron.

A. Almost all of the mass is concentrated in the nucleus.

Explanation:

Because when he shot the alpha particles towards the atoms, most passed through (which meant atom is mostly empty space), but some bounced back and such (which meant mass is concentrated in the nucleus.)

The reason they bounced is because alpha particles are postive and nucleus is positive as well, and we know positives don't attract, rather they repel thus they bounced.