Final answer:
Fluorine (F) has the smallest atomic radius among the given elements.
Step-by-step explanation:
The atomic radius, representing the size of an atom, generally follows predictable trends on the periodic table. Across a period, from left to right, the atomic radius tends to decrease due to an increased effective nuclear charge. This results from a higher number of protons in the nucleus, attracting the electrons more strongly and leading to a contraction of the atomic size. Conversely, down a group, from top to bottom, the atomic radius increases as new electron shells are added.
Considering the options:
a. B (Boron) is to the left of b. Al (Aluminum) and has a smaller atomic radius.
c. F (Fluorine) is to the right of d. N (Nitrogen) in the same period and has a smaller atomic radius.
Therefore, among the options provided, c. F (Fluorine) has the smallest atomic radius. Fluorine, being a highly electronegative element, experiences a strong pull on its electrons, resulting in a smaller atomic radius compared to the other elements listed. Understanding periodic trends is crucial in predicting and explaining variations in atomic size across the periodic table.