Here's why:

* Atomic Radius: Atomic radius generally increases as you move down a group on the periodic table and decreases as you move across a period from left to right.

* Location on Periodic Table: Sulfur (S) and Phosphorus (P) are both in the third period of the periodic table. Sulfur is located in Group 16, while Phosphorus is located in Group 15.

* Electron Shielding: As you move from left to right across a period, the number of protons in the nucleus increases, which attracts the electrons more strongly. This makes the atomic radius smaller.

Therefore, phosphorus, being further to the left on the periodic table, has a larger atomic radius than sulfur.