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Which element is radioactive, is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements. You can find this element in group 5A (15) directly to the right of the element that has 4 valence electrons in its 4th energy level.

User Pekpon
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Answer:

Astatine

Step-by-step explanation:

User Gintama
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