N the third period of the periodic table, sodium is followed by magnesium, aluminum, silicon, and phosphorus. Which of these elements has the smallest atomic size? sodium magnesium aluminum silicon phosphorus

You need to follow the atomic radius trend, the atomic radius decreases as you go across the period, and the atomic radius increases as you go down a group.

Between Sodium, Magnesium, Aluminum, silicon, and phosphorus, Sodium has the biggest atomic radius.