The answer is Strontium(Sr). The reactive increase from right to left. And this element has two valence electrons. So Rb is not correct. Then the very reactive metal is Sr.
If the moon did not rotate we would see all hemispheres of the moon as it revolves around the Earth and not just the phases.
The answer is 0.600 M; but I don't know how to get to that answer.
The answer to this is yes they are likely, true.
Answer:

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