Why would elements found in the same group on the periodic table have similar reactivity’s

A. They have the same number of protons
B. They have the same number of energy levels
C. They have the same atomic mass
D. They have the same number of valence electrons

D. They have the same number of valence electrons

Explanation:

In order to answer this question we need to understand the following.

Valence electrons refers to the outermost electron(s) in the outermost energy level of an atom.Elements in the same group in the periodic table have the same number of valence electrons. For instance, group 2A elements have 2 valence electrons.The reactivity of elements in the periodic table is based on the number of valence electrons and the ease of gaining or losing electrons.Elements in the same group have similar valence electrons and therefore share similar chemical properties such as reactivity.Hence, elements in the same group have same number of valence electron and will thus have similar reactivity.