Elements in the same group of the periodic table have similar properties because their electronic configurations have the same number of electrons in the outermost shell. Elemental behavior is almost completely reliant on this outermost shell configuration, with inner shells playing a less important role in determining properties. read more
Elements of the same group have the same kind of electronic configuration. The number of electrons in the outermost shell is the same. So the elements have to gain or lose the same number of electrons. This makes their properties similar. For example elements in the alkali metal group have one extra electron in their outermost shell. read more
Quick Answer. In the periodic table, elements in the same group or family have similar chemical properties because they have the same number of valence electrons in their outer shells. read more