Which compound is composed of oppositely charged ions? Please help me!

Question

\l "\l " A. SCl2

\l "\l " B. NH3

\l "\l " C. OCl2

\l "\l " D. Na2O

Answer 1

Sodium, with symbol Na is a.cation with a +1 charge. Oxygen, symbol O, is an anion with charge -2. When writing the formula cross the charges to the elements. Additionally, the cation  is always written first.