Neon (10Ne) possesses three stable isotopes: 20 Ne , 21 Ne , and 22 Ne . In addition, 17 radioactive isotopes have been discovered, ranging from 15 Ne to 34 Ne , all short-lived. The longest-lived is 24 Ne with a half-life of 3.38(2) min. All others are under a minute, most under a second. The least stable is 15 Ne with a half-life of 770(300) ys (7.7(3.0)×10−22 s). See isotopes of carbon for notes about the measurement. Light radioactive neon isotopes usually decay to fluorine or oxygen, while heavier ones decay to sodium.
^( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^# – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
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