The elements in alkali metal and halogen groups of the periodic table are the most reactive since they only need to gain or lose one electron to become stable by filling their valence orbital. What happens to reactivity, moving down the column of a group?

A) Reactivity stays the same because they are in the same group.

B) Reactivity increases because the valence level is further from the nucleus of the atom.

C) Reactivity decreases because the increased number of protons and electrons provides more stability.

Eliminate

D) Reactivity stays the same because the number of electrons needed to fill the valence orbital remains the same.

Reactivity increases because the valence level is further from the nucleus of an atom.

Explanation: The reactivity of elements in the periodic table depends on the position of the element in the periodic table. The trend in the reactivity across the period and down the group depends on whether one is dealing with metallic elements or non-metallic elements. Reactivity of metals such as alkali metals and alkali-earth metals increases down the group as the number of energy levels increases making valence electrons to be further from the nucleus. Reactivity of non-metallic groups such as halogen decreases down the group as energy levels increase which reduces the nuclear attraction of the valence electrons to the nucleus.