Valence electrons are the electrons in the outer most shell of the atom. The periodic table is arrange such that the columns represent the number of valence electrons. Column 1 and 2 elements have 1 and 2 valence electrons respectively. Columns 13 through 18 have 3 through 8 valence electrons respectively. The transitional metals, columns 3 through 12 don’t follow this exactly you need to use the d electron count method.