Here's why:

* The nucleus is not a single particle. It's a structure within an atom composed of two types of particles: protons and neutrons.

* Protons carry a positive charge. Neutrons, as their name suggests, have no charge.

* Therefore, the nucleus itself has a positive charge, determined by the number of protons it contains. This is because the positive charges of the protons outweigh the neutral charge of the neutrons.

In summary:

* The nucleus is a structure, not a particle.

* The nucleus contains positively charged protons.

* The nucleus itself has a positive charge.