Proton

Later experiments showed that the positive charge of a nucleus could be subdivided into a whole number of smaller particles, each carrying the same amount of positive charge. These particles were named protons. Nuclear charge could therefore be understood as the combined charge of its protons, rather than as an unexplained continuous positive region.

The discovery of the proton, a positively charged particle, explained the nucleus’s positive charge. Positive charge was no longer represented as a continuous material spread through the atom: it belonged to particles within the nucleus.