Identify how many of the original parent nuclei remain after three half-lives

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.

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explanation:

space exploration has led to the development and technological improvement of many everyday items. (if this answer is wrong i will find the right answer) : )