Elements in the same group on the periodic table have the same

number of electrons

number of protons

number of neutrons

number of valence electrons

Elements in the same group have the same number of valence electrons labelled in Roman numerals.

Also, From left side-Right side of the periodic is in the following order - Alkali Metals, Alkali Earth Metals, Halogens then Noble gases in the Far right of the periodic table