Which of the following is the most reactive element of group 17?

Fluorine

The correct answer is option 3. Fluorine.

Group 17 of the periodic table consists of elements known as the halogens. These elements include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Among these elements, fluorine is the most reactive.

The reactivity of an element is often determined by its ability to gain or lose electrons to achieve a stable electron configuration. In the case of fluorine, it has seven valence electrons and requires only one more electron to complete its outer electron shell and achieve the stable electron configuration of the nearest noble gas, which is neon.

Because of this strong desire to gain an electron, fluorine exhibits extremely high reactivity. It readily reacts with a wide range of other elements, including metals, nonmetals, and even noble gases, to form various compounds. Fluorine's high reactivity stems from its high electronegativity and small atomic size, which make it highly attractive to electrons.

In summary, fluorine is the most reactive element in Group 17 because of its strong tendency to gain electrons and form bonds with other elements, making it a highly reactive nonmetal.