There are three primary isotopes of hydrogen. Unlike any of the other isotopes, they have special names. Protium, Deuterium, and Tritium. No other isotopes have unique names.
Protium can also be called Hydrogen-1, Deuterium Hydrogen-2, and Tritium Hydrogen-3. These can even be abbreviated as H-1, H-2, and H-3.
There is another reason hydrogen is special. The most common isotope, protium doesn’t have any neutrons. It is the only element that doesn’t have neutrons.
There is one final way hydrogen is different from isotopes. Since hydrogen only had one proton, when we add neutrons it makes a big change in the mass. Add a neutron to protium to get deuterium and you’ve doubled the mass of the atom.
So while most isotopes of an element, like Cl-35 and Cl-37 have similar chemical and physical behaviors, isotopes of hydrogen have more pronounced differences in their chemical and physical properties.
