Step 1: Understand what atomic radius means. Atomic radius is the distance from the nucleus of an atom to the outermost shell of electrons.
Step 2: Know that atomic radius can vary among different elements. Generally, it decreases as you move from left to right across a period in the periodic table.
Step 3: Recognize that helium is located at the top right of the periodic table, which is where elements have the smallest atomic radii.
Step 4: Learn that helium has a high effective nuclear charge, meaning the positive charge from the nucleus pulls the electrons closer, resulting in a smaller radius.
Step 5: Note that helium has only two electrons, which means there is minimal electron shielding, allowing the nucleus to exert a strong pull on the electrons.
