* Positively charged particles located in the nucleus of the atom.

* The defining characteristic of an element. The number of protons in an atom (its atomic number) determines what element it is. For example, all carbon atoms have 6 protons.

* Contribute to the atom's mass. Protons have a mass of approximately 1 atomic mass unit (amu).

Important Note: In a neutral atom, the number of protons is equal to the number of electrons. This ensures that the atom has no overall electric charge.