Final answer:
Based on periodic table trends, the element with the largest atomic radius among the options is b. potassium.
Step-by-step explanation:
Atomic radius refers to the size of an atom, and it generally increases as you move down a group and decreases as you move across a period on the periodic table. In this case, calcium and potassium are in the same group (Group 2) and aluminum and fluorine are in the same period (Period 3).
As you move down Group 2 from calcium to potassium, the atomic radius increases due to the addition of electron shells. Potassium, being lower in the group, has a larger atomic radius compared to calcium. On the other hand, as you move across Period 3 from aluminum to fluorine, the atomic radius decreases. Fluorine, being on the rightmost side of the period, has the smallest atomic radius among these elements.
Therefore, potassium has the largest atomic radius among the options provided. Understanding periodic trends allows us to predict variations in atomic size based on the element's position in the periodic table. (Option B)