2.1Chemical Bonding, Application Of Chemical Reactions and Organic Chemistry

Bonding, Structure and Properties — WJEC GCSE Chemistry Revision Notes & Topical Questions

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Complete PDF with figures and original page layoutPage 1 WJEC GCSE Chemistry Your notes 2.1 Bonding, Structure & Properties Contents Properties of Substances Metallic Bonding Ionic Bonding Giant Ionic Structures Covalent Bonding Intermo…

Section 1 of 21Types of substance and bulk properties

Types
- ionic, metallic, simple molecular covalent and giant covalent
Bulk properties
- electrical conductivity and melting or boiling points come from many particles acting together, not from single atoms

Type	Example	Conducts?	Melting / boiling point	Explanation
Ionic	Sodium chloride	No when solid, yes when molten or aqueous	High	Strong electrostatic attraction between oppositely charged ions; ions free to move when molten or dissolved
Simple molecular	Carbon dioxide	No	Low	Weak intermolecular forces; no free charged particles
Giant covalent	Graphite, diamond, fullerenes	No (except graphite and fullerenes)	High	Strong covalent bonds between atoms; graphite and fullerenes have delocalised electrons
Metallic	Copper, sodium	Yes	High	Strong attraction between metal ions and delocalised electrons; electrons free to move

Section 2 of 21Metallic bonding

Structure
- metals have giant lattices in which atoms lose their outer electrons and become positive metal ions
Delocalised electrons
- the outer electrons belong to no one atom and form a "sea of electrons"
Metallic bond = the strong force of attraction between positive metal ions and delocalised electrons
Occurrence
- in metals and alloys, which are mixtures of metals

Section 3 of 21Properties of metals

High melting and boiling points
- strong electrostatic forces between the ions and delocalised electrons need a lot of energy to break
Conduction
- delocalised electrons move through the whole structure and carry charge, so metals conduct heat and electricity
Malleability
- layers of ions slide over each other when a force is applied, so metals can be hammered into shape
Higher tier
- melting point increases across a period
  - (sodium, magnesium, aluminium)
- The number of delocalised electrons increases.
- The attraction to the positive ions is greater, so more energy is needed.
Wording
- electrons move "through" the structure, not "throughout" it

Section 4 of 21Formation of ions

Ion = a charged atom or group of atoms formed by loss or gain of electrons
Purpose
- to obtain a full outer shell, so Group 1, 2, 6 and 7 ions have a noble gas configuration
Cations
- positive ions formed when atoms lose electrons, so they have more protons than electrons
Anions
- negative ions formed when atoms gain electrons, so they have more electrons than protons
Pattern
- metals lose electrons and non-metals gain electrons
Charge
- it equals the number of electrons lost or gained, so Mg loses 2 to give 2+ and Br gains 1 to give 1-
Ionic bond
- the strong electrostatic attraction between oppositely charged ions holds an ionic compound together

Section 5 of 21Dot and cross diagrams for ionic compounds

Purpose
- they show the arrangement of electrons in the compound
Notation
- electrons from one atom are dots and from the other are crosses, so transfer is clear
Charges
- each ion is in brackets with its charge at the top right
Sodium chloride
- sodium transfers its outer electron to chlorine, giving [Na]⁺ and [Cl]^- with a full outer shell of 8

Section 6 of 21Giant ionic structures

Lattice
- a regular arrangement of alternating positive and negative ions, tightly packed
Forces
- strong electrostatic attraction acts in all directions between oppositely charged ions
Models
- ball-and-stick and 3D space-filling models represent the lattice
High melting and boiling points
- the strong forces in all directions need a lot of energy to overcome
Solid conductivity
- ions are in fixed positions, so solids are poor conductors
Molten or dissolved conductivity
- ions can move and carry charge
Higher tier
- greater ion charge means a stronger force and a higher melting point
- Magnesium oxide (Mg²⁺ and O^2-) melts higher than sodium chloride (Na⁺ and Cl^-).
Wording
- say the ions move and carry charge, not that electrons do

Section 7 of 21Covalent bonding

Covalent bond = the sharing of a pair of electrons between non-metal atoms
Purpose
- each atom gains a full outer shell, giving a noble gas configuration
Structures
- covalent substances may be small molecules or giant molecules
Dot-and-cross diagrams
- electrons from one atom are dots and from the other are crosses, with shared electrons in the overlap of the shells
Single bonds
- each pair of adjacent atoms shares one pair
- Hydrogen, chlorine, water, methane, ammonia and hydrogen chloride all have single bonds.
- The first shell holds only 2 electrons.
Higher tier
- multiple bonds
- A double bond is two shared pairs, as in carbon dioxide and oxygen.
- A triple bond is three shared pairs, as in nitrogen.

Section 8 of 21Simple molecular structures

Structure
- molecules of just a few atoms, such as carbon dioxide and methane
Two types of bond
- strong covalent bonds between atoms in a molecule, and weak intermolecular forces between molecules
Low melting and boiling points
- weak intermolecular forces need little energy to overcome, and the covalent bonds do not break
Size trend
- larger molecules have stronger intermolecular forces, so melting and boiling points generally rise
Conductivity
- they are poor conductors even when molten because there are no free ions or electrons
Insulators
- most covalent compounds do not conduct in the solid state, such as the plastic around wiring, rubber and wood

Section 9 of 21Giant covalent structures and diamond

Giant covalent structure
- billions of non-metal atoms, each joined to its neighbours by covalent bonds
Carbon forms
- diamond and graphite contain only carbon but have different bonding, so their properties differ
Diamond structure
- each carbon bonds to four others in a tetrahedral arrangement
- All the bonds are identical and very strong.
Diamond properties
- It does not conduct, because all outer electrons are held in the four bonds, so no charge can move.
- It has a very high melting point, because strong covalent bonds need a lot of energy to break.
- It is extremely hard and dense, which makes it useful in cutting tools such as drills.
Hard against strong
- diamond is hard but brittle, and the opposite of hard is soft, not weak

Section 10 of 21Graphite

Structure
- each carbon bonds to three others in layers of hexagons, leaving one electron per atom delocalised
Bonds
- covalent bonds within layers are very strong, but weak intermolecular forces hold the layers together
Properties
- It conducts electricity, because delocalised electrons between the layers move through the structure and carry charge.
- It has a high melting point, because strong covalent bonds need a lot of energy to break.
- It is slippery, because the layers slide over each other on weak forces.
Uses
- pencils and industrial lubricant
Name
- pencil "lead" is graphite and has nothing to do with the metal lead

Section 11 of 21Fullerenes

Structure
- carbon atoms in caged structures
Buckminsterfullerene
- C₆₀ has 60 carbons forming 20 hexagons and 12 pentagons in a hollow sphere shaped like a football
Uses
- Trapping molecules inside the cage, which makes them useful for targeted drug delivery.
- A huge surface area to hold catalyst molecules so reactants can reach them.
- Lubricants, because of weak intermolecular forces between fullerenes.
Linking property to use
- drug delivery relies on the hollow shape

Section 12 of 21Graphene

Structure
- a single layer of graphite, a continuous hexagonal sheet one atom thick, so it is essentially 2D
Strength and lightness
- it is extremely strong and amazingly light, because the unbroken pattern of strong covalent bonds is hard to break
Conductivity
- it conducts heat and electricity because it has delocalised electrons
Uses
- composite materials and electronics

Section 13 of 21Carbon nanotubes

Structure
- graphene rolled into a cylinder, a type of fullerene
Properties
- High tensile strength and low density, resisting breaking and stretching.
- They conduct electricity, because each carbon bonds to three others and the spare electron is delocalised.
- High melting point, because of strong covalent bonds.
Uses
- composites, specialised materials, electronics and nanotechnology
Scale
- nanotubes are much smaller than the carbon fibres used in bikes and tennis rackets

Section 14 of 21Bulk properties of carbon forms

Bulk properties
- melting and boiling points, electrical and thermal conductivity, flexibility and hardness
Origin
- they come from the type and strength of bonds and the arrangement of atoms, not from individual atoms

Form	Key bulk properties
Diamond	Cannot conduct, extremely hard, high melting point
Graphite	Conducts electricity, soft and slippery, high melting point
Fullerenes	Can conduct electricity, good lubricant
Carbon nanotubes	High tensile strength, conduct electricity and heat
Graphene	Extremely strong, conducts, almost transparent

Diamond against graphite
- in diamond each carbon has four strong bonds so it is very hard,
- but in graphite each has three bonds in layers with weak forces between them so it is soft and slippery

Section 15 of 21Nanoparticles and silver

Bulk silver
- a shiny, malleable metal that does not corrode, mainly used in jewellery
Silver nanoparticles
- 1–100 nm in diameter with a large surface area to volume ratio, and they are antibacterial, antifungal and antiviral
Uses
- deodorant, the inside of fridges, and socks, to kill bacteria that cause odours
Principle
- the properties of a bulk material differ from those of its atoms because they come from bonding or from the surface area to volume ratio

Section 16 of 21Nanoparticles

Size
- 1 to 100 nanometres, usually a few hundred atoms, and atoms and simple molecules are about 100 times smaller
Nanoscience
- research into producing and applying nanoparticles
Surface area to volume ratio
- it is very high, and increases by a factor of 10 when the side of a cube decreases by a factor of 10
Consequences
- nanoparticles may have properties different from the same material in bulk, and smaller quantities may be needed to be effective

Section 17 of 21Silver nanoparticles

Properties
- they are antibacterial and antifungal, killing microorganisms without harming humans and other organisms
Sports clothing
- killing skin bacteria reduces body odour
Surgical equipment
- they kill bacteria on surfaces before operations
Fridges
- as an antibacterial coating, they kill bacteria that cause odours

Section 18 of 21Titanium dioxide nanoparticles

Property
- they reflect UV light but let visible light pass through
Transparent sunscreens
- They block UV, reducing the chance of sunburn and skin cancer.
- They cannot be seen on the skin because the particles are so small.
Self-cleaning windows
- Windows are coated with the nanoparticles.
- They break down dirt when sunlight UV shines on them.
- They make water spread in a thin film instead of droplets, which cleans the glass.
Syllabus note
- silver and titanium dioxide are the two named nanoparticles whose uses must be learned

Section 19 of 21Risks of nanoparticles (Higher tier)

Early stage
- use is new, so many factors and risks are unknown, especially the health effects
Skin absorption
- nanoscale silver in deodorants and titanium dioxide in sunscreens are applied to skin and could be absorbed
Entering the body
- they are so small that they could enter living cells or the bloodstream
Time scale
- no serious short-term side effects have been found, but long-term effects may not yet be detected
Toxicity
- a small toxicity is multiplied by the high surface area to volume ratio, and the body does not easily dispose of them,
- so caution is needed in medicine

Section 20 of 21Smart materials: photochromic and thermochromic

1More

Smart material = a material whose properties change reversibly, such as shape that returns to normal when conditions change

2Photochromic pigments2 points

they change colour with light intensity
Photochromic lenses darken in UV light, so they act as sunglasses in sun and normal glasses otherwise.

3Thermochromic pigments2 points

"thermo" is heat and "chroma" is colour, so they change colour with temperature
They are used in colour-changing mugs and strip thermometers.

Section 21 of 21Smart materials: polymer gels and shape memory

Polymer gels
- they absorb up to 1000 times their own volume of water
- Water molecules join weakly to the polymer chains, so the gel swells.
- They release the water slowly in dry conditions.
- Uses include nappies and soil granules that help plants retain water.
Shape-memory alloys
- alloys that return to their original shape on heating
  - (mixtures of metals)
- Used in sports helmets and car bodies.
- Used in surgical plates joining bone fractures, where body warmth applies tension for quicker healing.
Shape-memory polymers
- they can be bent but return to shape when heated
- Used in car bumpers, helmets and gum-shields.
Exam focus
- choose the most appropriate smart material for a situation rather than recall specific uses

Last updated: 14 October 2026

🌳 Student Search Tree & Frequently Asked Exam Questions: bonding, structure and properties

Step-by-step problem-solving guide, mark scheme criteria, and experimental error analysis curated by Dr. Khaled Dabour (DABOURHUB).

Q1: How to solve bonding, structure and properties examination questions step-by-step?

1. Identify all given values and convert non-standard units, 2. State the primary formula or physiological/chemical principle, 3. Calculate to 3 significant figures and clearly state units.

Q2: What are the common mistakes and experimental sources of error for bonding, structure and properties?

Avoid confusing independent vs dependent variables in practical questions. In calculation questions, double-check percentage change formula: (change / original) × 100.

🔍 Related Student Searches & Problem Trees for bonding, structure and properties:

Where can I find bonding, structure and properties past paper questions by topic with the mark scheme?

On DABOURHUB every bonding, structure and properties question is grouped by syllabus point and shown with the mark-scheme wording, so you can see exactly which sentence earns the mark instead of scrolling through whole year papers.

What is the most common bonding, structure and properties exam question and why do students lose marks on it?

The repeated pattern on IGCSE papers is a short stem that asks you to apply bonding, structure and properties and then justify it with a command word (explain, suggest, compare). Marks are lost by stating the fact without linking it back to the wording of the question, so each bonding, structure and properties item here is written as a full-mark answer.

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Yes: the bonding, structure and properties notes, topical questions and MCQ quizzes on this site follow the same syllabus headings as the official specification, and they open straight from the search result with no download step.

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