Ionic bonds form in compounds between which types of atoms?

• A. A noble gas and a metal
• B. Two nonmetals
• C. Two metals
• D. A metal and a nonmetal

Answer: (D)

Ionic bonds form when electrons are transferred from a metal to a nonmetal, creating a positively charged metal ion and a negatively charged nonmetal ion. The attraction between these opposite charges is what holds the compound together. Metals tend to lose electrons because they have low ionization energy, while nonmetals tend to gain electrons because they have high electron affinity. This transfer leads to an electrostatic bond that is characteristic of compounds formed between a metal and a nonmetal. For example, common salts like table salt (sodium chloride) arise from this metal–nonmetal pairing. In contrast, a noble gas and a metal would not typically form an ionic bond because noble gases are already stable and unlikely to transfer or accept electrons; two nonmetals usually form covalent bonds by sharing electrons, and two metals form metallic bonds with delocalized electrons rather than a transfer to create ions.