Covalent bonds typically form between nonmetals. Based on the provided options:
- Potassium (K) is a metal, and iodine (I) is a nonmetal.
- Magnesium (Mg) is a metal, and sulfur (S) is a nonmetal.
- Nitrogen (N) and oxygen (O) are both nonmetals.
- Sodium (Na) is a metal, and bromine (Br) is a nonmetal.
The pair that is most likely to form covalent bonds with each other is nitrogen (N) and oxygen (O), as both elements are nonmetals.