Explain why Francium is the most reactive Group 1 element in terms of its electronic structure.

All group 1 elements have 1 electron in their outer shell, making this the electron that is involved in reactions. As you move down a group in the periodic table the number of shells increases, which means that the outer electron is further from the nucleus. As there are now more shells between the electron and the nucleus, the outer electron experiences more shielding and therefore less attraction to the nucleus. This means that the outer electron is more easily removed in Francium than other group 1 elements.