Formation of Ions

• • Atoms need a full outer shell of electrons in order to be stable. One way they can achieve this is by gaining or losing electrons. 
  • Those that gain electrons become ions with a negative charge, whilst those that lose electrons become ions with a positive charge
• Magnesium loses electrons to become an ion

  Mg ➔ Mg2+ + 2e-
• Atoms which need to gain or lose only 1-2 electrons are more likely to become ions, compared to those which need to gain or lose 3-4.

  This is because gaining or losing electrons requires a lot of energy