| Answer | Crossword Clue |
|---|---|
| protium | an isotope of hydrogen |
| tritium | an isotope of hydrogen |
| protiums | PROTIUM, an isotope of hydrogen |
| tritiums | TRITIUM, an isotope of hydrogen |
| tritium | isotope of hydrogen having an atomic weight of three |
| deuterium | heavy hydrogen, an isotope of hydrogen of double mass |
| deuteriums | DEUTERIUM, heavy hydrogen, an isotope of hydrogen of double mass |
