Na, Mg and A1 are the elements of the same period of Modern Periodic Table having one, two and three valence electrons, respectively

Na, Mg and A1 are the elements of the same period of Modern Periodic Table having one, two and three valence electrons, respectively. Which of these elements
(i) has the largest atomic radius,
(ii) is least reactive? Justify your answer stating reason for each case.

(i) On going from left to right in the periodic table, atomic radius decreases due to increase in nuclear charge which pulls the outermost electron closer to the nucleus. Therefore, sodium has the largest atomic radius.

(ii) On going from left to right in the periodic table, the reactivity decreases due to increased nuclear charge which makes the loss of outermost electron by the element difficult. Therefore, aluminium is the least reactive element.