* Protons: The number of protons in an atom defines its atomic number. Chlorine (Cl) has an atomic number of 17, meaning it has 17 protons. This number stays the same regardless of whether the atom is neutral or an ion.
* Electrons: A neutral chlorine atom has 17 electrons (equal to the number of protons). However, a chloride ion (Cl⁻) has gained one extra electron. This means it has 18 electrons.
In summary:
* Protons: 17
* Electrons: 18
