Question

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1. The two rarest naturally occurring elements are astatine (At. Element 85) and francium (Fr, element 87). Both are very short-lived, undergoing radioactive decay rapidly. For astatine, the longest-lived isotope is 210 At, with a half-life of 8.1 hours. For francium, the longest- lived isotope is 223Fr, with a half-life of 22 minutes. Despite 210 At having a longer half-life than 223Fr, there is much less astatine than francium on Earth (approximately 1 ounce of astatine compared to 30 ounces of francium). Offer an explanation for why there is so little astatine present when it is more stable than francium. Hint: look up the decay chains for different elements (Th, Ac, U, Np). (5 points)