The most active of all the chemical elements is a halogen known as

a. iodine.

B. bromine.

C. fluorine.

D. astatine.

C. Flourine

Flourine is a pale yellow glass. It is the least dense and the most active chemically. It displaces other halogens from their compounds and also displaces oxygen from water. Bromine is liquid with a dark red color. Chlorine is more dense and less reactive than fluorine. It is a yellow-green gas. Iodine is a solid, grayish black in color and is the least chemically active among the halogens. Among the nonmentals though, only oxygen is more reactive than iodine.