Where are most of an atom's mass?

Question

Where are most of an atom's mass?

Answer 1

In its nucleus.

Answer 2

In the nucleus.

The electrons weigh hardly anything compared to the protons and neutrons.

It's all about Rutherford's (I think that was his name) gold foil experiment. Look into it :)

Answer 3

In the nucleus.

The nucleus is composed of Protons and Neutrons, collectively nucleons.

Electrons which make up the rest of an atom have a mass only 1/1820 of a proton, much much smaller by mass.