Which of the following groups have seven valence electrons and are very reactive?

Column 1 alkali metals
Column 2 alkaline earth metals
Column 17 halogens
Column 18 noble gases

Column 17 halogens

Explanation:

To answer the question we need to know the following;

What are valence electrons?

Valence electrons are outermost electrons in the outermost energy level of an atom of any element.

What are halogens?

Halogens are group 7 elements that have seven valence electrons. They include, chlorine, fluorine, iodine, etc

What is the reactivity of halogens?

Halogens are the most reactive non-metals in the periodic table. They react by gaining one electron to attain a stable configuration.