Definition:

An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net positive or negative charge.

Key Points:

• Atoms or Molecules: Ions can be formed from either atoms or molecules.
• Electron Gain or Loss: Ions are formed when an atom or molecule gains or loses electrons.
• Net Charge: The gain or loss of electrons gives ions a net positive or negative charge.
• Positive Ions (Cations): Ions that have lost electrons and therefore have a positive charge are called cations.
• Negative Ions (Anions): Ions that have gained electrons and have a negative charge are called anions.
• Formation: Ions can be formed through various processes such as chemical reactions, ionizing radiation, or dissolving in solvents.

Example:

An example of a common ion is the sodium ion (Na+), which is formed when a sodium atom loses an electron.