Formation of ions

• Ions

  Charged particles - can be single atoms (e.g. Cl-) or groups of atoms (e.g. NO3-)
• Formation of ions

  1. Atoms lose or gain electrons to form ions

  2. Atoms try to get a full outer shell like a noble gas

  3. Metals lose electrons to form positive ions (cations)

  4. Non-metals gain electrons to form negative ions (anions)
• The number of electrons lost or gained is the same as the charge on the ion
• Groups most likely to form ions

  • Group 1
  • Group 2
  • Group 6
  • Group 7
• Elements in the same group all have the same number of outer electrons, so they form ions with the same charge
• Ions formed by elements

  • Sodium atom (Na) forms sodium ion (Na+)
  • Magnesium atom (Mg) forms magnesium ion (Mg2+)
  • Chlorine atom (Cl) forms chloride ion (Cl-)
  • Oxygen atom (O) forms oxide ion (O2-)
• Atoms form ions to achieve a full outer electron shell, which is a stable electronic structure