Ionic Bonding (Edexcel GCSE Chemistry: Combined Science)

Sodium Chloride Dot & Cross Diagram

• The process of ion formation does not happen in isolation; sodium atoms want to lose electrons and chlorine atoms want to gain electrons
• We can use dot & cross diagram to show this as one continuous process
• The positive and negative charges are held together by the strong electrostatic forces of attraction between oppositely charged ions
• This is what holds ionic compounds together

Sodium chloride ionic bonding

Magnesium Oxide Dot & Cross Diagram

• Magnesium is a group 2 metal so will lose two outer electrons to another atom to have a full outer shell of electrons
  • A positive ion with the charge 2+ is formed

• Oxygen is a group 6 non-metal so will need to gain two electrons to have a full outer shell of electrons
• Two electrons will be transferred from the outer shell of the magnesium atom to the outer shell of the oxygen atom
• The oxygen atom will gain the two electrons
  • A negative ion with charge 2- is formed

Diagram showing the dot-and-cross diagram of magnesium oxide

• Ionic compounds are made of charged particles called ions which form a giant lattice structure
• A lattice is a regular repeating arrangement of particles, in this case, ions
• Ionic substances have high melting and boiling points due to the presence of strong electrostatic forces acting between the oppositely charged ions
• These forces act in all directions and a lot of energy is required to overcome them

Strong electrostatic forces act in all directions in an ionic solid such as sodium chloride