Explain why reactivity increases as you go down group 1 (alkali metals) of the periodic table (3 marks)

As you go down the group, there is an additional electron shell added each time (1). These electron shells hold negatively charged electrons that shield the positive nucleus from the outer shell electron. (1) This therefore reduces the attraction between the outer shell electron and the nucleus, meaning the electron can be removed more easily (making it more reactive). (1)