An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

• A. Atom
• B. Ion
• C. Element
• D. Molecule

Answer: (B)

When electrons are gained or lost, the balance of charge changes because electrons carry negative charge. If electrons are lost, there are more protons than electrons, giving a positive charge. If electrons are gained, there are more electrons than protons, giving a negative charge. A species that has this net electric charge is called an ion. This can be a single atom that has become positively or negatively charged, or a charged collection of atoms, i.e., a polyatomic ion. An element is a pure kind of atom and can be neutral or ionized, but the term itself doesn’t specify charge. A molecule is two or more atoms bonded together and can be neutral or charged, but again, the term doesn’t inherently denote a charge. The key idea is that an ion is the charged form arising from electron loss or gain.