Which of the following pairs of elements is most likely to form an ionic compound?

nitrogen and sulfur

sodium and aluminum

magnesium and fluorine

oxygen and chlorine

Answer is d. oxygen and chlorine ...

Magnesium and Fluorine

Explanation:

An ionic compound is formed by the bond between a metal and a nonmetal element. The metal will donate electrons, and will become a cation; the nonmetal will gain electrons and will become an anion. The bond will be formed by electrostatic force.

On the periodic table, the nonmetals are the elements on groups 3A to 7A, except for the diagonal from Boron to Polonium.

So, Nitrogen and Sulfur are both nonmetals and form a covalent compound, the same as for Oxygen and Chlorine. Sodium and Aluminium are both metals and form a metal compound. Magnesium is a metal and Fluorine a nonmetal, they form an ionic compound.