Chlorine naturally exists as two isotopes, \(_{17 ... In other words, in every 100 chlorine atoms, 75 atoms have a mass number of 35, and 25 atoms have a mass number of 37.

and the sum of the protons and neutrons gives the atomic mass, the number of neutrons defines the isotope of that element. For example, most carbon (≈ 99 %) has 6 protons and 6 neutrons and is written ...

This is because the number of electrons determines chemical properties, and all three isotopes have one electron in their atoms. An isotope is named after the element and the mass number of its atoms.

This Section implements all activities of the IAEA's Water Resources Programme, which promotes and transfers know-how on the use of isotope hydrology as an effective tool for water resources ...