Chemistry · Unit 4

Chemical Bonding

How atoms join together

Bonding is the whole of chemistry in one question: why do atoms stick together, and what does the resulting arrangement behave like?

The unit covers ionic, covalent and metallic bonding, giant versus simple molecular structures, and the weaker intermolecular forces that explain why water is a liquid at room temperature when much heavier molecules are gases.

This unit breaks down into 20 short steps and 120 questions, starting at difficulty 1 and building to 3. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.

Steps: 20
Questions: 120
Difficulty: 1-3

What this unit covers

Ionic Bonding
Covalent Bonding
Metallic Bonding
Giant and Simple Structures
Intermolecular Forces

Where this fits

Needs Atoms and The Periodic Table. Underpins almost every unit after it.

Where people slip

Bond strength and melting point are not the same question. Simple molecular substances have strong covalent bonds inside each molecule and weak forces between them, and it is the weak ones that melting has to overcome.

How the unit is structured

Chemical Bonding runs as 20 short steps that unlock in order. 15 are practice rounds and 5 are challenge rounds that pull together everything before them. Questions start at difficulty 1 and climb to 3 as you progress.

Step 1 · easierStep 20 · harder

Challenge rounds

Example questions

30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 120 in the unit altogether.

Covalent Bonding

Multiple choiceLevel 1
1. A covalent bond forms when...
- Two non-metal atoms share a pair of electronscorrect
- A metal gives its electrons to a non-metal
- Two metal atoms pool their electrons
- Atoms lose all of their electrons
Covalent bonds are shared pairs of electrons between non-metal atoms.
Build the sentenceLevel 2
2. Build the definition of electronegativity.
Answer: the power of an atom to attract bonding electrons
Electronegativity is the ability of an atom to attract the shared pair of electrons in a covalent bond.
Fill the blankLevel 2
3. In a nitrogen molecule, N2, the two atoms share three pairs of electrons, forming a ____ bond.
- triplecorrect
- single
- double
- ionic
Nitrogen atoms share three electron pairs, giving a strong triple bond.
Guess the numberLevel 2
4. How many electrons in total are shared in a single covalent bond?
Answer: 2 electrons
A single covalent bond is one shared pair, which is two electrons.
Match the pairsLevel 2
5. Match each molecule to its chemical formula.
Answer: Water = H2O; Carbon dioxide = CO2; Methane = CH4; Ammonia = NH3
Water is H2O, carbon dioxide is CO2, methane is CH4 and ammonia is NH3.
Odd one outLevel 3
6. Three of these molecules are polar overall. Which one is the odd one out because it is non-polar?
- CO2correct
- H2O
- NH3
- HCl
CO2 has two polar C=O bonds, but its linear symmetry makes the bond dipoles cancel, so the molecule is non-polar.

Giant and Simple Structures

Build the sentenceLevel 2
7. Arrange the words to complete the sentence about carbon nanotubes: as well as being strong, they can ____ ____ ____ heat.
Answer: conduct electricity and
Carbon nanotubes are not only very strong but can also conduct electricity and heat.
Choose all that applyLevel 2
8. Which properties make graphite suitable for use as an electrode? (Choose all that apply.)
- It conducts electricitycorrect
- It has a very high melting pointcorrect
- It is transparent
- It burns easily at room temperature
Graphite conducts because of its delocalised electrons and withstands very high temperatures, so it works well as an electrode.
Fact or fibLevel 2
9. Graphite is soft and slippery because its layers are held together by weak forces and can slide over one another.
Answer: True
Weak London forces between graphite's flat layers let them slide apart easily, which is why graphite works as a lubricant and in pencils.
Fill the blankLevel 2
10. In graphite each carbon atom bonds to three others, leaving one ____ electron per atom that lets graphite conduct electricity.
- delocalisedcorrect
- shared
- transferred
- ionic
Graphite's spare delocalised electron can move and carry charge, so graphite conducts electricity.
Guess the numberLevel 3
11. Pure silicon is a semiconductor with a diamond-like giant covalent structure. In the modern periodic table (groups 1-18), which group is silicon in?
Answer: 14 group
Silicon is in group 14, so like carbon it forms four covalent bonds in a giant lattice.
Match the pairsLevel 3
12. Match each form (allotrope) of carbon to its key feature.
Answer: Diamond = Hardest, each carbon bonded to four others; Graphite = Conducts electricity, layers slide; Graphene = Single sheet one atom thick; Fullerene C60 = Hollow cage-shaped molecule
Diamond is the hardest, graphite conducts and slides in layers, graphene is a one-atom-thick sheet, and C60 is a hollow cage molecule.

Intermolecular Forces

Multiple choiceLevel 1
13. Why do simple molecular substances have low boiling points?
- The weak forces between the molecules are easily overcomecorrect
- The covalent bonds inside the molecules are very weak
- They contain free-moving ions
- They have a giant lattice structure
Boiling only needs to overcome the weak forces between molecules, so little energy is required.
Picture questionLevel 1
14. 💧 This is water, H2O. It is made of small, separate molecules. What type of substance is it?
- A simple molecular substancecorrect
- A giant ionic compound
- A metal
- A giant covalent structure
Water is made of small, separate H2O molecules, so it is a simple molecular substance.
Choose all that applyLevel 2
15. Hydrogen bonding occurs when hydrogen is directly bonded to which highly electronegative atoms? Select all that apply.
- Fluorinecorrect
- Oxygencorrect
- Nitrogencorrect
- Carbon
Hydrogen bonds form only when H is bonded to nitrogen, oxygen or fluorine, the three most electronegative atoms with lone pairs.
Fact or fibLevel 2
16. Longer-chain alkanes have higher boiling points than shorter ones because they have stronger London dispersion forces.
Answer: True
Longer chains have more electrons and a larger surface area of contact, so the dispersion forces between molecules are stronger.
Fill the blankLevel 2
17. Simple molecular substances have low melting points because the ____ forces between the molecules are weak.
- intermolecularcorrect
- covalent
- ionic
- metallic
The weak intermolecular forces need little energy to overcome, giving low melting points.
Put in orderLevel 3
18. For molecules of similar size, order these intermolecular forces from weakest to strongest.
Answer: London dispersion forces -> Permanent dipole-dipole forces -> Hydrogen bonds
For comparable molecules the strength usually rises from London dispersion, to permanent dipole-dipole, to hydrogen bonding.

Ionic Bonding

Multiple choiceLevel 1
19. Ionic bonds usually form between which two types of element?
- A metal and a non-metalcorrect
- Two non-metals
- Two metals
- Two noble gases
Ionic bonding happens when a metal transfers electrons to a non-metal, forming charged ions.
Choose all that applyLevel 2
20. Which of these are typical properties of ionic compounds? (Choose all that apply.)
- High melting and boiling pointscorrect
- Conduct electricity when molten or dissolvedcorrect
- Often form solid crystalscorrect
- Conduct electricity well as solids
Ionic compounds have high melting points and form crystals, and only conduct when molten or dissolved - not as solids.
Fill the blankLevel 2
21. The ions in sodium chloride are arranged in a regular, repeating 3D pattern called a giant ionic ____.
- latticecorrect
- molecule
- chain
- droplet
Ionic compounds are held in a giant lattice of alternating positive and negative ions.
Put in orderLevel 2
22. Put the steps of forming sodium chloride (NaCl) in the correct order.
Answer: A sodium atom loses one outer electron -> A chlorine atom gains that electron -> A positive Na+ ion and a negative Cl- ion form -> The oppositely charged ions attract and build a giant lattice
Sodium transfers an electron to chlorine, and the resulting Na+ and Cl- ions attract to build a giant lattice.
Odd one outLevel 3
23. Three of these cations have a fairly low polarising power. Which one is the odd one out, with a much greater polarising power?
- Al3+correct
- Na+
- K+
- Rb+
Al3+ is small and highly charged, so it distorts nearby anions far more strongly than the singly charged ions.
True or falseLevel 3
24. A Born-Haber cycle works because the total enthalpy change from the elements to the ionic solid is the same whichever route is taken (Hess's law).
Answer: True
Hess's law lets the direct formation route be equated with the multi-step route through gaseous ions.

Metallic Bonding

Fact or fibLevel 1
25. Metals are usually good conductors of both heat and electricity.
Answer: True
The delocalised electrons let metals carry heat and electricity well.
Fill the blankLevel 1
26. Metals can conduct electricity because they contain ____ electrons that are free to move.
- delocalisedcorrect
- fixed
- paired
- trapped
The delocalised (free-moving) electrons carry electric charge through the metal.
Multiple choiceLevel 1
27. Metallic bonding is best described as...
- A lattice of positive metal ions surrounded by a sea of delocalised electronscorrect
- Pairs of electrons shared between neutral atoms
- Electrons transferred from one atom to another
- Neutral atoms held together by gravity
In a metal, positive ions sit in a sea of shared, delocalised electrons.
True or falseLevel 1
28. In metallic bonding, the outer electrons stay tightly attached to their own individual atoms.
Answer: False
The outer electrons become delocalised and are free to move throughout the whole piece of metal.
Build the sentenceLevel 2
29. Arrange the words to complete the description: in a metal, positive ions are held together by a ...
Answer: sea of delocalised electrons
Metallic bonding is positive ions held together by a sea of delocalised electrons.
Odd one outLevel 2
30. Which one is NOT a typical property of metals?
- Poor conductor of electricitycorrect
- Malleable
- Good conductor of heat
- Shiny when freshly polished
Metals are good conductors of electricity, so being a poor conductor is the odd one out.

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.

How you practise

This unit mixes 17 different question formats, so you are recalling and applying rather than recognising the same layout every time.

Build the sentence
Choose all that apply
Fact or fib
Fill the blank
Guess the number
Listen and choose
Match the pairs
Multiple choice
Odd one out
Picture question
Put in order
Sequence recall
Sort into groups
Spell it
Tap the pairs
True or false
Type the answer

Practise Chemical Bonding

120 questions across 20 steps. Start with step one and crawl at your own pace.

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Read about Chemical Bonding

Explainers from our blog on what this unit covers. Each one ends with real questions from the bank.

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