What is the difference between a molecule and an ion?

What is the difference between a molecule and an ion?

• A. A molecule is a neutral group of atoms bonded together; an ion carries a net charge.
• B. An ion is a neutral group of atoms bonded together; a molecule carries a net charge.
• C. A molecule contains only metals; an ion contains nonmetals.
• D. A molecule cannot form bonds; an ion can.

Answer: (A)

The main idea here is that net electric charge is what separates a molecule from an ion. A molecule is a neutral group of atoms bonded together, typically held by covalent bonds, so it carries no overall charge. An ion forms when an atom or a group of atoms gains or loses electrons, giving the species a net positive or negative charge. That difference in charge is what defines them: neutral molecules like water, oxygen (O2), etc., versus charged ions like sodium ion (Na+) or chloride ion (Cl−). Some groups of atoms can be charged as a unit (polyatomic ions like sulfate, SO4^2−), and those are ions rather than neutral molecules. The other statements don’t fit because ions are not neutral, molecules aren’t restricted to metals, and molecules can indeed form bonds.

The main idea here is that net electric charge is what separates a molecule from an ion. A molecule is a neutral group of atoms bonded together, typically held by covalent bonds, so it carries no overall charge. An ion forms when an atom or a group of atoms gains or loses electrons, giving the species a net positive or negative charge. That difference in charge is what defines them: neutral molecules like water, oxygen (O2), etc., versus charged ions like sodium ion (Na+) or chloride ion (Cl−). Some groups of atoms can be charged as a unit (polyatomic ions like sulfate, SO4^2−), and those are ions rather than neutral molecules. The other statements don’t fit because ions are not neutral, molecules aren’t restricted to metals, and molecules can indeed form bonds.