[{"hint": "Think about how many types of atoms are involved.", "answer": "An element is one type of atom; a compound is two or more elements bonded together.", "question": "What is the difference between an element and a compound?"}, {"hint": "Na is a metal, Cl is a nonmetal.", "answer": "Ionic — metals and nonmetals form ionic bonds by transferring electrons.", "question": "Is NaCl (table salt) an ionic or covalent compound?"}]