halogen

"The chlorine in the swimming pool keeps it clean. "

"The prisoners were kept in a secure compound. "

"Clouds were forming interesting shapes in the sky. "

"Due to its extreme radioactivity and rarity, astatine is mostly studied in specialized laboratories and has no common uses in everyday life. "

"Letters are the elements of written language."

"The house was surrounded by a tall fence. "

"The atmosphere was thick with the smell of popcorn, as the kids gathered for the movie night. "

"The lightbulb's filament glowed brightly. "

"The science experiment used bromine, a reddish-brown liquid with a strong odor. "

"The mechanic fixed the broken bicycle chain. "

"Because fluorine is so reactive, it is often used to create stronger compounds like those found in Teflon and some toothpastes. "

"The teacher gave a good example of a sentence using the past tense. "