Why do elements in the same group or column of the periodic table have similar properties? A. They have the same number of protons. B. They have the same number of neutrons. C. They have the same number of outer shell electrons. D. They have the same number of electron shells.

The Answer is C. The outer shell electrons are the electrons which are involved with chemical reactions and bonding. All elements in the same group have different number of total electrons but ALL have the same number of outer shell electrons. This is why they exhibit similar chemical properties.