What two things do valance electrons control

Explanation:

Now using this information, we are looking for which has a full outermost shell AKA full capacity of valence electrons. For the 1st element, it should have 2 because the inner shell is also the outermost in this case. Since only 1 valence electron is present, it is not full. The second element, has 2 shells and thus should have 8 in the outermost shell, but only 3 are present in this case. So its not the 2nd one. The third atom does satisfy the conditions- making it the answer. The fourth is wrong because 3 shells are mentioned and so the outermost would need to have 18 valence electrons.

hopefully this helped, it took me age to write ahah