Here's why:

* Elements are defined by the number of protons. All atoms of a particular element have the same number of protons in their nucleus. For example, all carbon atoms have 6 protons.

* Atoms of the same element can have different numbers of neutrons. These are called isotopes. For example, carbon-12 has 6 neutrons, while carbon-14 has 8 neutrons.

* Electrons are also part of atoms. While the number of electrons in a neutral atom is equal to the number of protons, atoms can gain or lose electrons, forming ions.

So, while atoms of the same element can have different numbers of neutrons and electrons, they all share the same number of protons.

Let me know if you'd like to know more about isotopes or ions!