For a given odd mass number, there can be only a single beta-stable nuclide, since there is not a difference in binding energy between even–odd and odd–even comparable to that between even–even and odd–odd, leaving other nuclides of the same mass number (isobars) free to beta decay toward the lowest-mass nuclide.
fɚɹə ɡˈɪvən ˈɑːd mˈæs nˈʌmbɚ, ðɛɹ kæn biː ˈoʊnli ɐ sˈɪŋɡəl bˈeɪɾəstˈeɪbəl nˈuːklaɪd, sˈɪns ðɛɹ ɪz nˌɑːɾə dˈɪfɹəns ɪn bˈaɪndɪŋ ˈɛnɚdʒi bᵻtwˌiːn ˈiːvən ˈɑːd ænd ˈɑːd ˈiːvən kˈɑːmpɚɹəbəl tə ðæt bᵻtwˌiːn ˈiːvən ˈiːvən ænd ˈɑːd ˈɑːd, lˈiːvɪŋ ˈʌðɚ nˈuːklaɪdz ʌvðə sˈeɪm mˈæs nˈʌmbɚ ˈaɪsəbˌɑːɹz fɹˈiː tə bˈeɪɾə dᵻkˈeɪ təwˈɔːɹd ðə lˈoʊɪstmˈæs nˈuːklaɪd.