Ionic Bonding – GCSE Chemistry Revision (AQA Additional Science – Double and Triple)

Why bond?

  • Elements react with other elements because they ‘want’ to end up with a full outer electron shell
  • Electrons surround the nucleus of an atom in shells – remember Atomic Structure. The shells go (2,8,8) when full
  • Getting the full shell will make them very stable
  • The noble gases on the far right of the periodic table are like this – they don’t react with anything very much because they already have full shells
  • Atoms can get a full shell by:
  • Losing or gaining electrons in ionic bonding
  • Sharing electrons in covalent bonding


  • Ionic bonding happens between metals and non-metals
  • Sodium and Chlorine can react together – they bond ionically to produce sodium chloride (table salt)
  • Sodium’s electron shells go (2,8,1) – all its shells are full except the outer one, which only has a single electron in it… if it can get rid of that electron, its new outer shell will be full
  • Chlorine’s shells go (2,8,7) – it just needs one more electron; then all its shells will be full
  • The solution to this problem is for sodium to give its spare electron to chlorine – then everyone’s happy, so to speak… both atoms are now stable

The Consequences

  • However, the balance of charges has been shifted!
  • Normally, an atom has an equal amount of protons and electrons
  • Electrons are negatively charged, and protons are positively charged, but they cancel each other out meaning the atom is neutral overall
  • But this doesn’t happen after ionic bonding
  • The sodium atom has sacrificed an electron to gain its outer shell – this means it has more protons than electrons, so the atom now has an overall positive charge
  • Likewise, the chlorine atom has gained an electron, so it has more electrons than protons, and it has an overall negative charge


  • The sodium and chlorine atoms have become ions
  • An ion is an atom which has lost or gained an electron and thus has a charge
  • The sodium is now a positive ion and the chlorine is now a negative ion
  • And you know what happens to positives and negatives!
  • Opposites attract – the ions get stuck together by their electrostatic charges!
  • That’s why they call it ionic bonding

Magnesium and Oxygen

  • Magnesium goes (2,8,2) – it needs to get rid of that 2 in its outer shell
  • Oxygen goes (2,6) – it needs two more electrons to fill up
  • So magnesium donates its two spare electrons to oxygen
  • Because magnesium has lost TWO electrons, it now becomes an ion with a positive charge of 2 (because it has two more protons than electrons)
  • Oxygen has gained two electrons, so it becomes an ion with a negative charge of two
  • They bond together as usual
  • Don’t forget that gaining electrons gets you a negative charge
  • Losing electrons gets you a positive charge

Potassium and Oxygen

  • Potassium’s electron shells go (2,8,8,1) – it really needs to get rid of that ONE pesky electron hogging its outer shell
  • As I’ve said, oxygen goes (2,6) – it needs to gain TWO electrons
  • So if the potassium gives the oxygen its spare electron it’s happy – it becomes a stable potassium ion with a full outer shell and a single positive charge
  • BUT, the oxygen atom is not satisfied – it still needs one more electron to fill up its outer shell
  • What are we gonna do?! Well, the solution is to bring in a second potassium atom
  • Like its friend was, this new potassium atom is looking to lose one electron
  • After gives an electron to oxygen, everything is fine – the two potassium ions both have single positive charges, and the oxygen has become an ion with a full outer shell and a double negative charge
  • The three ions stick together – not so much because of their gratitude, but because of the strong electrostatic force that’s now bonding them
  • So the moral of the story is, sometimes it takes two atoms to get the right amount of electrons

About Matt

I like writing, filmmaking, programming and gaming, and prefer creating media to consuming it. On the topic of consumption, I'm also a big fan of eating.
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One Response to Ionic Bonding – GCSE Chemistry Revision (AQA Additional Science – Double and Triple)

  1. Pingback: Covalent Bonding, Structures and Properties – GCSE Chemistry Revision (AQA Additional Science – Double and Triple) | Matt's blog

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