sodium, atomic radius increases as we go down and right in the periodic table, which means that cesium is the element with the biggest atomic radius as it is located as the farthest bottom right of the periodic table, anyways, the atomic number of aluminum is 13 which means that the distribution of electrons here is K:2, L:8, M:3,, number of levels = the atomic period which the atom is located in, last number in the last electronic level (or the valency) = the atomic group which the atomic is located in, so in this case aluminum is located in group 3 period 3 at the periodic table, we have to find the atom which is located the nearest to the bottom right using the same method, sodium is located in group 1 period 3, boron is located in group 3 period 2, silicon is located in group 4 period 3, nitrogen is located in group 5 period 2,,, so the correct answer is sodium as it’s located at the left of aluminum and closer to the left of the periodic table, albeit being in the same period