Which statement correctly matches a bond type with its defining characteristic?

• A. Covalent bonds involve electron sharing; high melting points and conduct electricity when molten.
• B. Ionic bonds involve electron transfer; high melting points and conducts electricity when molten.
• C. Metallic bonds involve a delocalized electron sea; they are brittle and insulate electricity.
• D. Ionic bonds involve electron sharing; low melting points and does not conduct electricity.

Answer: (B)

Ionic bonds form when electrons are transferred from a metal to a nonmetal, creating oppositely charged ions held together by electrostatic attraction. This creates a strong crystal lattice with a very high melting point. In the solid state the ions are fixed in place, so the substance doesn’t conduct electricity; when melted, the ions can move and carry charge, so it does conduct. Covalent bonds involve sharing electrons, not transfer, which usually leads to lower melting points and poor electrical conductivity for most covalent compounds. Metallic bonds involve a sea of delocalized electrons, which makes metals good conductors and malleable rather than brittle. So the description that matches an ionic bond with electron transfer, high melting points, and conduction when molten is the best fit.