Question

which element is reactive an element whose atoms atoms have seven valence electrons or a element whose atoms have eight valence electrons explain

Answer 1

Elements with 7 valence electrons are extremely reactive, while elements with 8 valence electrons practically don't react at all.

This is caused by the fact that all molecules want to have 8 valence electrons; that's just the scientific fact. So, if an element already has 8 valence electrons, it doesn't need to react with anything. If the element only has 7 valence electrons, however, it really wants to react with something with 1 valence electron to get to that special number 8.