What is an ion and how does ionic bonding form compounds?

• A. An ion is an atom with a positive or negative charge; ionic bonding forms when electrons are transferred from a noble gas to a metal.
• B. An ion is a neutral molecule that moves freely in a lattice.
• C. An ion is an atom with a positive or negative charge; ionic bonding occurs when electrons are transferred from a non-metal to a metal.
• D. An ion is an atom with a positive or negative charge; ionic bonding occurs when electrons are transferred from a metal to a non-metal, forming oppositely charged ions that attract.

Answer: (D)

An ion is an atom that has gained or lost electrons to become charged. In ionic bonding, a metal tends to lose electrons and a non-metal tends to gain them. This transfer creates a positively charged metal ion (cation) and a negatively charged non-metal ion (anion). The opposite charges attract strongly, pulling the ions together to form an ionic bond and a solid ionic compound with a regular lattice structure. This is why the correct description says electrons move from a metal to a non-metal, forming oppositely charged ions that attract. The other ideas aren’t how ionic bonding works: noble gases don’t typically donate electrons to metals, an ion is not a neutral molecule, and the transfer described as from a non-metal to a metal is the reverse of what happens.