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Ionic bonding follows electron transfer and is the strong attraction between opposite ions in a giant lattice. Covalent bonding shares electron pairs. Metals contain positive ions attracted to delocalised electrons. A dot-and-cross diagram tracks outer electrons; it is not a literal picture of electron colour or size. Ionic formulae have balanced total positive and negative charge, so Mg2+ with Cl⁻ gives MgCl2.
Video by Cognito. The video’s own board label is retained; follow the specification reference and scope notes on this lesson for assessed content.
Viewing focus: Describe ionic, covalent and metallic bonding
After watching, attempt these questions before opening the answers. You can also use the written lesson below.
After watching 1: What carries current in molten sodium chloride?
Mobile ions. Melting frees ions to move.
After watching 2: What holds a simple molecular substance together within each molecule?
Covalent bonds. Melting usually overcomes attractions between the molecules.
What you'll be able to do
Ionic bonding follows electron transfer and is the strong attraction between opposite ions in a giant lattice. Covalent bonding shares electron pairs. Metals contain positive ions attracted to delocalised electrons. A dot-and-cross diagram tracks outer electrons; it is not a literal picture of electron colour or size. Ionic formulae have balanced total positive and negative charge, so Mg2+ with Cl⁻ gives MgCl2.
An ionic solid does not conduct because its ions cannot move, but a molten or dissolved ionic substance can conduct through mobile ions. Metals conduct through delocalised electrons. Simple molecular substances often have low melting points because the attractions between molecules are weak compared with covalent bonds. Giant covalent materials need many strong bonds overcome, giving high melting points.
Diamond has four covalent bonds per carbon and a rigid network. Graphite has three bonds per carbon, layers that slide, and delocalised electrons that conduct along the layers. Graphene is one carbon layer; fullerenes include hollow molecular structures. Nanoparticles have high surface area relative to volume, which can improve catalysis and coatings, but their small size can introduce exposure risks. A useful evaluation connects a particular property to a particular application.
Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.
Common mistakes to avoid
Key takeaways
Question 1: Write the formula of aluminium oxide from Al3+ and O2−.
Al2O3.
Check the assessed scope and practical or mathematical requirements.
An external explanation or interactive activity to use alongside the lesson. It may include extension material.
Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.