Question

Which element in Period 3 is the most active nonmetal?

Answer 1

Chlorine. The most active nonmetal in any period is second to last (halogens), right before the noble gases.

Explanation:

Atoms tend to give electron (metals) or take them (nonmetals) to achieve a stable configuration such as a noble gas (like argon) already has. If taking just one electron makes the atom's electron configuration like a noble gas, you have an active nonmetal. That's what elements right before the noble gases like chlorine, called halogens (Greek for salt-formers) do.