What are covalent structures in the context of chemical bonding?

Covalent structures refer to the arrangement of atoms that are bonded together by sharing pairs of electrons. This type of chemical bonding is known as covalent bonding, where atoms achieve stability by filling their outer electron shells. Covalent structures can be simple molecules like water (H2O) or complex networks like diamond. Understanding covalent structures is crucial in the IB MYP Science curriculum as it explains how atoms combine to form various substances.

How do covalent bonds differ from ionic bonds?

Covalent bonds involve the sharing of electron pairs between atoms, typically between nonmetals, to achieve stability. In contrast, ionic bonds result from the transfer of electrons from one atom to another, usually between a metal and a nonmetal, leading to the formation of charged ions. This fundamental difference in electron interaction is a key concept in the IB MYP Science curriculum when studying chemical bonding.

What are some examples of covalent structures?

Examples of covalent structures include simple molecules like oxygen (O2) and carbon dioxide (CO2), as well as giant covalent structures like diamond and graphite. In these structures, atoms are bonded by shared electrons, forming either discrete molecules or extensive networks. These examples are often explored in the IB MYP Science curriculum to illustrate the diversity of covalent bonding.

Why are covalent structures important in everyday life?

Covalent structures are fundamental to many substances that are essential in everyday life. For instance, water, a simple covalent molecule, is vital for all known forms of life. Organic compounds, which are primarily covalent, form the basis of all living organisms. Understanding these structures helps students in the IB MYP Science curriculum appreciate the role of chemistry in the natural world and technology.

What is the significance of molecular geometry in covalent structures?

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule, which is determined by the covalent bonds and lone pairs of electrons. This geometry affects the physical and chemical properties of the substance, such as polarity, reactivity, and phase of matter. In the IB MYP Science curriculum, students learn how to predict and explain molecular shapes using models like VSEPR theory, which is crucial for understanding the behavior of covalent compounds.

Why is "Confusing allotropes with isotopes." a common mistake in Covalent Structures?

Why it happens: Both sound similar. How to avoid it: ALLOTROPES = different structures of the same ELEMENT (diamond vs graphite). ISOTOPES = different mass numbers of the same ELEMENT (¹²C vs ¹⁴C).

Why is "Thinking giant covalent structures melt easily because each bond is 'just' a covalent bond." a common mistake in Covalent Structures?

Why it happens: Students associate covalent compounds with low MPs. How to avoid it: Simple covalent molecules HAVE weak intermolecular forces and low MPs. But giant covalent structures have MANY strong covalent bonds extending throughout — very high MPs.

Chemical bondingIB MYP Sciences (Years 1-5)

Covalent Structures

Work through the notes, try the practice questions, then take the quiz. The report tells you exactly what to revise next.

Previous Next

Learn this Topic

Start with the slides for the quick version, then go deeper with the full study notes.

Short Study Notes in the form of Slides

Read the notes first. If the method in a worked example clicks, you're ready for the questions.

Short Study Notes — Covalent Structures

Start with these resources to cover the key concepts, then work through the practice questions.

Page 1 / 0

Detailed Notes

Full prose, callouts and a recap — built for A* mastery, not just a quick scan.

Take these study notes with you

Download a branded PDF — full prose, callouts, recap and memorise list for Covalent Structures, ready to print or save offline.

Covalent Structures — IB MYP Sciences: giant covalent structures, diamond, graphite and graphene

When MANY atoms link together with covalent bonds, you don't get a small molecule — you get a giant network. This MYP Sciences note covers diamond, graphite, graphene, fullerenes and silicon dioxide, and why they have such striking and varied properties.

What you’ll learn

Mapped to the IB MYP Sciences subject guide (2026 onwards).

MYP Sciences A — Describe the structure and bonding in diamond, graphite, graphene and silicon dioxide.
MYP Sciences A — Link structure to properties: hardness, conductivity, slipperiness.
MYP Sciences D — Evaluate uses of carbon allotropes (drill bits, pencils, electrodes, drug delivery).

Diamond and graphite — two faces of carbon

Same element, different arrangements, wildly different properties.

Diamond and graphite are both made of pure carbon — but their atoms are arranged completely differently, giving radically different properties. They are allotropes of carbon.

Diamond. Every carbon atom forms FOUR strong covalent bonds to its neighbours, in a 3D tetrahedral lattice. Result:

Extremely hard — strong bonds throughout the structure. Used in drill bits, cutting tools.
Very high MP (~3 700 °C) — millions of covalent bonds to break.
Doesn't conduct electricity — all four outer electrons are used in bonding (no free electrons).

Graphite. Each carbon forms THREE bonds, in flat hexagonal LAYERS. The fourth outer electron is delocalised within the layer. Result:

Soft and slippery — layers slide easily over each other. Used in pencils and as a dry lubricant.
Very high MP — covalent bonds INSIDE layers are very strong.
CONDUCTS electricity in the plane of the layers — delocalised electrons can move. Used as electrodes.

Diamond's tetrahedral 3D bonding makes it the hardest natural substance; graphite's stacked flat layers make it slippery and a conductor.

Diamond: 4 bonds per C, 3D lattice, very hard, doesn't conduct.
Graphite: 3 bonds per C, flat layers, soft and slippery, conducts.
Both very high MP — covalent bonds are strong.

Graphene and fullerenes

Modern carbon allotropes with extreme properties.

Graphene is a single layer of graphite — one atom thick. Discovered in 2004 (Geim and Novoselov, Nobel Prize 2010). Properties:

About 200× stronger than steel by weight.
Excellent electrical conductor.
Flexible and almost transparent.
Potential uses: flexible screens, super-fast electronics, lightweight composites.

Fullerenes are hollow carbon structures shaped like spheres, tubes or cages:

C₆₀ (buckminsterfullerene) is a spherical 60-carbon-atom 'buckyball'.
Carbon nanotubes are rolled-up graphene sheets.

Both are studied for drug delivery (loading molecules inside the cage), lubricants and conducting materials.

Graphene: 1 layer of graphite. Strong, flexible, transparent, conducts.
C₆₀ buckyball: 60-atom hollow sphere.
Carbon nanotubes: rolled-up graphene sheets.

Silicon dioxide and other giant covalent

SiO₂ (quartz, sand) is the silicon equivalent of diamond.

Silicon dioxide (SiO₂) — quartz, the main component of sand and glass — has a giant covalent structure similar to diamond. Each Si is bonded to 4 O atoms; each O is bonded to 2 Si atoms. Result:

Hard.
Very high MP (~1 700 °C).
Doesn't conduct (no free electrons).
Insoluble in water.

Used in glass, computer chips (after purification), abrasives, electronic components.

Note that despite the SAME bonds as in CO₂, the structure is completely different — SiO₂ forms a giant lattice while CO₂ exists as separate small molecules. The difference is in how Si and C behave: Si forms longer, less-stable double bonds, so it prefers single bonds in a 3D network.

SiO₂: each Si bonded to 4 O; each O bonded to 2 Si.
Giant lattice → hard, high MP, no conductivity.
Used in glass, chips, abrasives.

How it’s examined

Criterion A tests structures and properties. Criterion D often asks for an evaluation of why a particular use suits a particular structure (e.g. why diamond in drill bits, graphite in pencils).

Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.

Master this Topic

Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.

Take this whole topic with you

Download a branded revision sheet — worked examples, formulae, definitions and common mistakes for Covalent Structures, ready to print or save as PDF.

Step-by-step worked examples — Covalent Structures

Step-by-step solutions to past-paper-style questions on covalent structures, written exactly the way a tutor would explain them at the board.

1Why does graphite conduct?
Building confidence• graphite, conductivity
Question
Explain why graphite conducts electricity but diamond does not.
Step-by-step solution
1. Step 1
  In graphite, each C forms 3 bonds, leaving ONE outer electron free per atom — these electrons are delocalised across each layer.
2. Step 2
  Delocalised electrons can flow → graphite conducts within the layers.
3. Step 3
  In diamond, each C uses ALL 4 outer electrons in covalent bonds — no free electrons, so no conduction.
Answer
Graphite has delocalised electrons (free to move within layers). Diamond uses all 4 outer electrons in bonding, so no free electrons → no conduction.
2Why is diamond so hard?
Building confidence• diamond
Question
Explain why diamond is the hardest natural substance.
Step-by-step solution
1. Step 1
  Diamond's structure is a 3D lattice in which every carbon is bonded to 4 others by strong covalent bonds.
2. Step 2
  To scratch or break diamond you have to break many of these strong bonds in all directions — extremely difficult.
Answer
3D lattice of carbons each bonded to 4 others by strong covalent bonds. To break or scratch diamond means breaking many of these strong bonds → very hard.
3Predicting melting points
Stretch• MP
Question
Predict whether silicon dioxide (SiO₂) has a higher or lower melting point than carbon dioxide (CO₂). Explain.
Step-by-step solution
1. Step 1
  SiO₂ has a GIANT COVALENT structure — many strong bonds throughout.
2. Step 2
  CO₂ has a SIMPLE MOLECULAR structure — small molecules held together by weak intermolecular forces.
3. Step 3
  Breaking SiO₂'s many strong covalent bonds needs much more energy than breaking CO₂'s weak intermolecular forces. So SiO₂'s MP >> CO₂'s.
Answer
SiO₂ has a MUCH higher MP. Giant covalent (many strong bonds) needs vastly more energy to melt than simple molecular (weak intermolecular forces).

Key Definitions and Keywords — Covalent Structures

Definitions to memorise and the exact keywords mark schemes credit for covalent structures answers — sharpened from recent examiner reports for the 2026 IB MYP Sciences sitting.

Allotrope
Examiner keyword
Different structural forms of the same element (e.g. diamond and graphite are allotropes of carbon).
Giant covalent structure
Examiner keyword
A structure where many atoms are bonded by covalent bonds extending throughout the lattice.
Delocalised electron
Examiner keyword
An electron not fixed to a particular atom; free to move and carry charge.
Graphite
Examiner keyword
A soft, conducting allotrope of carbon. Each C bonded to 3 others in flat layers; layers slide.
Diamond
Examiner keyword
The hardest natural substance. Each carbon bonded to 4 others in a 3D tetrahedral lattice.
Graphene
A single layer of graphite — one atom thick. Strong, flexible, transparent, conducts.
Fullerene
A hollow molecule of carbon shaped like a cage, sphere or tube (e.g. C₆₀, carbon nanotubes).

Common Mistakes and Misconceptions — Covalent Structures

The traps other students keep falling into on covalent structures questions — taken from recent IB MYP Sciences examiner reports and mark schemes — and how to avoid them.

✕Confusing allotropes with isotopes.
Why it happens
Both sound similar.
How to avoid it
ALLOTROPES = different structures of the same ELEMENT (diamond vs graphite). ISOTOPES = different mass numbers of the same ELEMENT (¹²C vs ¹⁴C).
✕Thinking giant covalent structures melt easily because each bond is 'just' a covalent bond.
Why it happens
Students associate covalent compounds with low MPs.
How to avoid it
Simple covalent molecules HAVE weak intermolecular forces and low MPs. But giant covalent structures have MANY strong covalent bonds extending throughout — very high MPs.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Covalent Structures — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

Covalent Structures

Short Study Notes in the form of Slides

Short Study Notes — Covalent Structures

Detailed Notes

What you’ll learn

How it’s examined

1Why does graphite conduct?

2Why is diamond so hard?

3Predicting melting points

Allotrope

Giant covalent structure

Delocalised electron

Graphite

Diamond

Graphene

Fullerene

✕Confusing allotropes with isotopes.

✕Thinking giant covalent structures melt easily because each bond is 'just' a covalent bond.

Practice questions

Past paper style quiz

Assess your understanding

Covalent Structures — frequently asked questions