Question

Which particle, when emitted from the nucleus of an atom, would have the greatest effect on the mass of the atom?

Answer 1

Consider the following.

Explanation:

The nucleus contains only protons and neutrons, so we would have to compare the mass of both of them.

Proton: `~~1.01 amu` or `1.6726 * 10^-27 kg`
Electron: `0.00055 amu` or `9.1 * 10^-31 kg`

As you can tell, a proton has much more mass than an electron, so it should have the greater effect on the mass of the atom.

However, emitting a proton does change the element of the atom, so I am not certain of which one actually affects the mass the greatest. It may possibly depend on the element of the atom itself!