Answer: Halogens
Explanation:
Halogens include elements like Fluorine, Chlorine, Iodine and Bromine. These elements can be dangerous to humans especially when used in large quantities.
When combined with other elements however, they can form very useful materials. Chlorine for instance forms salt when combined with sodium. Fluorine becomes very useful in toothpaste to protect teeth and bromine can be used in pesticides.
