All hydrogen atoms contain one proton (and one electron), but they can contain different numbers of neutrons. Hydrogen-1 is the most abundant isotope of hydrogen.
Ions are charged particles formed when atoms, or groups of atoms, lose or gain electrons:
The charge on an ion is shown as a superscript. For example, an aluminium ion Al3+ carries 3 positive charges. It forms when an aluminium atom loses 3 electrons.
When you calculate the number of subatomic particles in an ion, you need to take into account the number of electrons lost or gained.
The atomic number of a chloride ion, Cl-, is 17 and its mass number is 35. Calculate the number of protons, neutrons and electrons it contains.