Ion

Definition

An ion is an atom or molecule that has gained or lost one or more electrons, giving it a net positive or negative charge. Ions are crucial in various biological processes and chemical reactions.

5 Must Know Facts For Your Next Test

1. Ions are formed when atoms gain or lose electrons to achieve a full outer shell of electrons.
2. Positive ions, called cations, form when an atom loses electrons, while negative ions, called anions, form when an atom gains electrons.
3. Sodium (Na+) and chloride (Cl-) are common examples of cations and anions respectively.
4. Ions play essential roles in cell signaling, muscle contraction, and maintaining the balance of fluids in organisms.
5. In water, ionic compounds dissociate into their respective ions which can conduct electricity.

Review Questions

• What is the difference between a cation and an anion?
• How do ions contribute to the conduction of electricity in aqueous solutions?
• Why are ions important for biological processes such as muscle contraction?

Related terms

Electron: A subatomic particle with a negative charge that orbits the nucleus of an atom.

Cation: A positively charged ion formed by losing one or more electrons.

Anion: A negatively charged ion formed by gaining one or more electrons.