Here's why:

* Atoms are made up of three main subatomic particles: protons, neutrons, and electrons.

* Protons reside in the nucleus of the atom, along with neutrons.

* Protons carry a positive charge, while neutrons have no charge (they are neutral).

* Electrons orbit the nucleus and carry a negative charge.

The number of protons in an atom determines its atomic number and defines what element it is.