There are four possibilities silicon, phosphorus Chlorine and Argon.
Oxygen is in the second period while Sulfur is in the third period.
There are five non metal elements in the third period numbers 14-18
Silicon which is a metalloid Phosphorus , Sulfur, Chlorine and Argon.
The question might be what are the nonmetals in family VA
The three nonmetals in the same family are Oxygen , Sulfur, and Selenium Se # 34.
The question may be confusing families or groups with periods.