isotope
NUCLIDES HAVING THE SAME ATOMIC NUMBER BUT DIFFERENT MASS NUMBERS
Isotopes; Nuclear notation; Isotope notation; Chemical isotope; Ice otope; Isotopic notation; AZE notation; Index to isotope pages; Nuclide notation; Isotop
(isotopes)
Isotopes are atoms that have the same number of protons and electrons but different numbers of neutrons and therefore have different physical properties. (TECHNICAL)
...tritium, a radioactive isotope of hydrogen.
N-COUNT