Ionic compounds form between metals and nonmetals

Steps:

• Ionic compounds result from electron transfer between metals (low electronegativity) and nonmetals (high electronegativity).
• Classify elements: metals lose electrons; nonmetals gain them.
• Check pairs for one metal and one nonmetal.
• Select the pair meeting this criterion.

Why C is correct:

• Lithium (Group 1 metal) transfers electrons to oxygen (Group 16 nonmetal), forming Li₂O per ionic bonding rules.

Why the others are wrong:

• A: Carbon and hydrogen are both nonmetals; they share electrons covalently (e.g., CH₄).
• B: Hydrogen and chlorine are both nonmetals; they share electrons covalently (e.g., HCl).
• D: Sulfur and oxygen are both nonmetals; they share electrons covalently (e.g., SO₂).

Final answer: C