Nuclear Composition
The nucleus of aluminium comprises 27 nucleons: 13 protons and 14 neutrons. As protons have a positive electric charge, equal and opposite to that held by electrons, 13 electrons are needed to overcome the nucleus’s charge, and form one atom of aluminium. As protons and neutrons have approximately the same mass, each weighing almost 2,000 times as much as an electron, the mass of the orbiting electron body is negligible when compared to that of the nucleus.
IN2P3