Transcription: we need to quantify what we mean by stable and unstable nuclei. Nuclei qualify as stable if they can last longer than the age of the universe and we'll take that as meaning longer than 10 to the 11th years. At the other extreme, we'll say a nucleus is impossible if it can't hold itself together for as long as a millionth of a millionth of a second, that's 10 to the minus 12th of a second. Unstable nuclei are everything in between, so that's a very big range. we'll also assume that all the possible nuclei have been discovered and maybe that's not yet quite true.
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