Electrons have an electric charge of −1, which is equal but opposite to the charge of a proton, which is +1. All atoms have the same number of electrons as protons, so the positive and negative charges "cancel out", making atoms electrically neutral. Protons are found in the nucleus of the atom. This is a tiny, dense region at the center of the atom. Protons have a positive electrical charge of one (+1)(+1) and a mass of 1 atomic mass unit (amu)(amu), which is about 1.67×10−271.67×10−27 kilograms. Together with neutrons, they make up virtually all of the mass of an atom.