Terbium-147 undergoes positron emission to become a stable atom, the stable atom is ₆₄Gd¹⁴⁷.
Series (or family) of natural radioactive decay is the set of elements with unstable nuclei, which follow an orderly sequence of spontaneous decay, that is, they emit alpha and beta particles, until a stable lead nucleus is created.
In this case, natural radioactive decay occurs when the nucleus of the atom of some chemical element is unstable and then it "breaks", releasing electromagnetic radiation and disintegrating.
See more about radioactive decay at brainly.com/question/1770619
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