Which statement best differentiates ionic and molecular compounds?

• A. Ionic compounds form from metals and nonmetals by electron transfer.
• B. Molecular compounds form from metals and nonmetals by electron transfer.
• C. Ionic compounds are always covalent.
• D. Molecular compounds have high melting points.

Answer: (A)

The key idea is how bonds form between atoms. Ionic and molecular compounds differ in how electrons are arranged between atoms. Ionic compounds form when a metal donates electrons to a nonmetal, creating positively charged cations and negatively charged anions. The electrostatic attraction between these opposite charges holds the compound together in a solid lattice. This electron transfer is what sets ionic bonds apart from covalent bonds, where atoms—usually nonmetals—share electrons to fill their outer shells, resulting in discrete molecules rather than a lattice. Because ionic bonds involve a strong attraction between ions, ionic compounds typically have high melting points and can conduct electricity when melted or dissolved. So the statement that best differentiates the two is that ionic compounds form from metals and nonmetals by electron transfer. The other ideas either describe covalent bonding instead, claim ionic compounds are covalent, or generalize properties (like high melting points for molecular compounds) that aren’t universally true.