Isotopes are atoms of the same element (like Chlorine-35 and Chlorine-37) that have a different mass because they have a different number of protons electrons neutrons protons and neutrons
The element chlorine (Cl) has two isotopes: chlorine-35 and chlorine-37. 75.5% of chlorine atoms have 18 neutrons and 17 protons, and the other 24.5% have 20neutrons and 17protons.
