* Protons: These are positively charged particles. The number of protons in an atom defines its atomic number and determines what element it is.
* Neutrons: These are neutral particles, meaning they have no charge. The number of neutrons in an atom can vary, resulting in different isotopes of the same element.
Together, protons and neutrons make up almost all of the atom's mass, with the electrons contributing very little. The nucleus is extremely dense, containing nearly all of the atom's mass in a tiny volume.
