Explanation:

Let’s break it down:

- Actinides are those heavy metals at the bottom of the table—think uranium and thorium. They're used in nuclear stuff, not what you’re looking for.

- Chalcogens are the group with oxygen, sulfur, and selenium. They’re important, but fluorine, chlorine, and the gang aren’t here.

- Lanthanides are those rare earth metals, right next to the actinides. Stuff like europium and cerium. Cool for magnets, not for your question.

- Halogens—that’s fluorine, chlorine, bromine, iodine, and even astatine. They’re in Group 17 and are all super reactive nonmetals.

So, the real answer is:

Option 4: Halogen