Final answer:
Aluminum (Al) has the smallest atomic radius among the given elements due to its position on the periodic table, which gives it more protons and a stronger effective nuclear charge.
Step-by-step explanation:
The atom among the provided options that has the smallest atomic radius is Aluminum (Al). Atomic radius generally decreases across a period from left to right due to the increase in the number of protons in the nucleus, which results in a greater pull on the electron cloud, causing it to draw closer to the nucleus. In the periodic table, Aluminum (Al) is located to the right of Sodium (Na), Phosphorus (P), Arsenic (As), and is above Tellurium (Te), which means it has more protons and a stronger effective nuclear charge than these other elements, resulting in a smaller atomic radius.