Ions

• Ions are charged particles. They are created when an atom or molecule gains or loses electrons. Gaining electrons creates a negatively charged ion; losing electrons creates a positively charged ion.
• Positive ions (cations)

  • Positive ions are usually created when an atom or molecule loses electrons.
  • The metals in group 1 and 2 can easily lose electrons to become positively charged ions.

  
• Negative ions (anions)

  • Negative ions are usually created when an atom or molecule gains electrons.
  • The non-metals in group 7 are most likely to gain electrons to fill up their electron shell and become negatively charged.

  
• Ions containing multiple elements

  • Ions can be:
  • Single elements (e.g. F-).
  • A group of elements with an overall charge (e.g. SO42-).