Isotopes of hydrogen
The main isotopes of hydrogen are unique because they are the only isotopes that have a name. These names are still in use today. Deuterium and tritium sometimes get their own symbols, D and T. However, the International Union of Pure and Applied Chemistry does not like these names very much, even though they are often used. There are other isotopes that had their own names when scientists studied radioactivity. But, their names are no longer used today.