What’s a element that is a non metal, contains 7 valance electron, 3 energy levels?

The answer is Cl.

Group/family 18, the Nobel Gases, have full octets of 8 valence electrons. Each time you move to the LEFT one time within the nonmetals on the Periodic Table, an electron is lost. So, any element in group/family 17 would have 7 valence electrons (you can check this by drawing Bohr diagrams for each element within group/family 17).

So, we now know that the element is a nonmetal found in group/family 17. Therefore, it is found in the "p" block. For elements found in the "p" block, periods represent energy levels. 

answer: the primary difference between a hypothesis and a theory is that b hypothesis is falsifiable, but a theory has been proven to be correct. theory is an explanation of something that is happening but hypothesis is a guess of something that can happen

explanation: