Here's why:

* Location on the Periodic Table: Sulfur is located below oxygen in the same group (Group 16, also known as the chalcogens).

* Electron Shells: As you move down a group, elements have an additional electron shell. This means sulfur has one more electron shell than oxygen, which increases the distance between the nucleus and the outermost electrons.

* Shielding: The additional electron shells in sulfur also provide more shielding from the nucleus, reducing the effective nuclear charge experienced by the outer electrons. This further contributes to a larger atomic radius.

Therefore, sulfur has a larger atomic radius than oxygen.