Question

Element X has 7 valence electrons. How could this element react?

Answer 1

If the number of electrons in the L shell of X is 7, then its atomic number is 9 (as 2 electrons are in the K shell and 7 electrons are in L shell). 
Thus, the number of protons in X is 9 (equal to a number of electrons).
It can acquire a noble gas configuration by accepting one electron to complete its octet as it has 7 valence electrons.