Elements in the same family (or group) generally have similar properties because they have the same number of valence electrons in their outermost shell. This similarity in valence electron configuration leads to comparable chemical reactivity and bonding behavior among elements in the same group. Since chemical properties are largely determined by the electrons involved in bonding (the valence electrons), elements with the same number of these electrons exhibit similar physical and chemical properties such as reactivity, types of compounds formed, and general behavior in reactions.
