Understanding intermolecular forces, electron configuration, and acid-base reactions is crucial... Show more
Chemistry428 views·Updated May 21, 2026·4 pagesOCR A-Level Chemistry Guide
Caitlin @caitlin_05
1 / 4
1
of 4
Intermolecular Forces
Ever wondered why some substances melt easily whilst others need loads of heat? It's all down to intermolecular forces - the attractions between molecules that you'll need to master for your exams.
Induced dipole-dipole forces are the weakest type and occur in all molecules. Larger molecules like iodine have bigger electron clouds, creating stronger forces and higher boiling points. That's why straight-chain hydrocarbons have higher boiling points than branched ones - they can pack together more tightly.
Permanent dipole-dipole forces happen between polar molecules like HCl. These are stronger than induced forces because the molecules have permanent positive and negative ends. You can actually test for polar molecules by seeing if a liquid stream bends towards a charged rod!
Hydrogen bonding is the strongest intermolecular force and only occurs with nitrogen, oxygen, or fluorine. This explains why water has such unusual properties - hydrogen bonds make ice less dense than liquid water, which is why ice floats.
Quick Test Tip: Remember that when heating liquids, you're breaking intermolecular forces, not covalent bonds within molecules.
2
of 4
Molecular vs Ionic Properties & Electron Configuration
The type of bonding completely determines a substance's properties. Molecular substances like iodine and ammonia have low melting points because you're only breaking weak intermolecular forces. They don't conduct electricity and their water solubility depends on polarity.
Giant ionic compounds like sodium chloride behave totally differently. They're solid at room temperature with high melting points because you need massive energy to break strong electrostatic forces between ions. They conduct when liquid because ions can move freely.
Moving on to electron configuration - this might seem tricky, but it's just about filling electron "parking spaces" in order. The s subshell holds 2 electrons, p holds 6, d holds 10, and f holds 14. Remember that electrons prefer to occupy empty orbitals first before pairing up.
For ions, simply add or remove electrons from the highest energy level. Calcium (Ca) has 20 electrons, but Ca²⁺ has lost 2 electrons, giving it 18. Use noble gas notation like [Ar] 4s¹ for potassium to save time in exams.
Memory Trick: Higher shell numbers mean electrons are further from the nucleus and have higher energy levels.
3
of 4
Orbital Shapes
Orbitals aren't just abstract concepts - they're actual 3D regions where electrons hang out around the nucleus. Understanding their shapes helps explain how atoms bond and behave.
S orbitals are perfectly spherical, whilst p orbitals are dumbbell-shaped and come in three orientations (px, py, pz). When filling orbitals, electrons spin in opposite directions to minimise repulsion - think of it like they're trying to avoid each other!
The aufbau principle is your roadmap for electron configuration. Fill lower energy levels first, and remember that 4s fills before 3d (even though 3d is written first in the final configuration). For iron (Fe), you get: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s².
When atoms form ions, they lose or gain electrons to achieve stable configurations. This is fundamental to understanding chemical reactivity and bonding patterns you'll encounter throughout A-level chemistry.
Exam Success: Always check your electron numbers add up to the atomic number for neutral atoms!
4
of 4
Acids and Bases
Acids are proton donors and bases are proton acceptors - this Brønsted-Lowry definition is absolutely essential for A-level success. When acids and bases react, they're essentially swapping protons (H⁺ ions).
Strong acids like HCl, H₂SO₄, and HNO₃ completely dissociate in water, flooding the solution with H⁺ ions. Weak acids like ethanoic acid only partially dissociate, creating an equilibrium. The same principle applies to strong bases (NaOH, KOH) versus weak bases (NH₃).
Neutralisation reactions always follow the same pattern: acid + base → salt + water. The key reaction is H⁺ + OH⁻ → H₂O. You'll also need to know that metals react with acids to produce hydrogen gas, whilst metal carbonates produce carbon dioxide.
Polyprotic acids can donate multiple protons - monoprotic (like HNO₃), diprotic (like H₂SO₄), or triprotic (like H₃PO₄). This affects stoichiometry in calculations, so always check how many protons each acid can donate.
Equation Mastery: Learn the ionic equations - they show what's actually happening chemically and often earn extra marks in exams.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar content
Most popular content: Hydrogen Bonding
4ChemistryStructure & Bonding Overview
Explore the key concepts of metallic, ionic, and covalent bonding, including their structures, properties, and the effects of intermolecular forces. This summary covers the principles of bonding types, crystal structures, and the VSEPR theory, providing essential insights for AQA A Level Chemistry students. Ideal for exam preparation and understanding material properties.
1239216
ChemistryUnderstanding Intermolecular Forces
Explore the key concepts of intermolecular forces, including dipole-dipole interactions, hydrogen bonding, and Van der Waals forces. This summary provides insights into how these forces influence molecular shape, boiling points, and physical properties of substances. Ideal for students studying chemistry and looking to grasp the fundamentals of molecular interactions.
131693
ChemistryElectronegativity & Intermolecular Forces
Explore the concepts of electronegativity, dipole moments, and intermolecular forces including hydrogen bonding and van der Waals forces. This summary covers the nature of polar and non-polar bonds, the significance of dipole-dipole interactions, and how these factors influence the physical properties of substances. Ideal for AQA A Level & AS Chemistry students.
1219815
ChemistryUnderstanding Intermolecular Forces
Explore the key types of intermolecular forces, including London dispersion forces, dipole-dipole interactions, and hydrogen bonding. This summary highlights their mechanisms, strengths, and effects on physical properties like boiling points, tailored for AQA A-level Chemistry students.
1219410
Most popular content in Chemistry
9G
ChemistryGCSE AQA Chemistry Topic 1- The Atom
The Atom
109270
Chemistrychem paper 1
higher
111,79537
G
ChemistryGCSE AQA Chemistry Topic 1
Quiz covering all of topic 1
101,6583
ChemistryA-level OCR A Chemistry summary sheets
Everything from snaprevise for OCR chemistry a-level
121,99677
ChemistryEssential Chemistry Practicals
Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.
1011,775902
C
Chemistrychem paper 1
Unlock the secrets of chemical reactions with this comprehensive flashcard set designed to help you conquer complex concepts and ace your Chemistry exams.
115861
A
ChemistryAQA GCSE Chemistry 4.2 Bonding, structure and the Properties of Matter
4.2 Metals and Alloys
96740
A
ChemistryAQA GCSE Chemistry 4.4 Chemical changes
4.4 Reactions of acids with bases or carbonates
95521
F
ChemistryFundamentals of Atomic Structure
Practice identifying subatomic particles, calculating neutrons, and defining isotopes and atomic/mass numbers.
123400
Most popular content
9
SociologySociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
12101,9513,036
SociologySociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
1271,5982,281
English LiteratureAn Inspector Calls: Character Insights
Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.
1025,049896
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1251,7131,025
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
126,396118
CriminologyCriminology Theories Overview
Explore key criminology theories and their implications on crime and deviance. This comprehensive summary covers biological, psychological, and sociological perspectives, including labelling theory, right realism, and the impact of social campaigns on policy development. Ideal for A-Level criminology students seeking to understand the complexities of criminal behaviour and the factors influencing crime prevention strategies.
129,732211
English LiteratureRomeo and Juliet: Key themes
Key Romeo and Juliet themes and analysed quotes
106,561193
English LiteratureMacbeth: Guilt and Ambition
Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.
918,657387
BiologyAQA Biology: Key Concepts
Explore essential AQA Biology topics including Photosynthesis, Respiration, Homeostasis, Genetics, and Ecology. This comprehensive knowledge organizer covers key concepts such as energy transfer, hormonal control, and genetic variation, providing a solid foundation for your studies. Ideal for exam preparation and understanding biological processes.
108,325295
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user
Chemistry428 views·Updated May 21, 2026·4 pagesOCR A-Level Chemistry Guide
Caitlin @caitlin_05
Understanding intermolecular forces, electron configuration, and acid-base reactions is crucial for success in A-level chemistry. These fundamental concepts explain everything from why water forms ice to how atoms bond and react with each other.
1
of 4Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Intermolecular Forces
Ever wondered why some substances melt easily whilst others need loads of heat? It's all down to intermolecular forces - the attractions between molecules that you'll need to master for your exams.
Induced dipole-dipole forces are the weakest type and occur in all molecules. Larger molecules like iodine have bigger electron clouds, creating stronger forces and higher boiling points. That's why straight-chain hydrocarbons have higher boiling points than branched ones - they can pack together more tightly.
Permanent dipole-dipole forces happen between polar molecules like HCl. These are stronger than induced forces because the molecules have permanent positive and negative ends. You can actually test for polar molecules by seeing if a liquid stream bends towards a charged rod!
Hydrogen bonding is the strongest intermolecular force and only occurs with nitrogen, oxygen, or fluorine. This explains why water has such unusual properties - hydrogen bonds make ice less dense than liquid water, which is why ice floats.
Quick Test Tip: Remember that when heating liquids, you're breaking intermolecular forces, not covalent bonds within molecules.
2
of 4Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Molecular vs Ionic Properties & Electron Configuration
The type of bonding completely determines a substance's properties. Molecular substances like iodine and ammonia have low melting points because you're only breaking weak intermolecular forces. They don't conduct electricity and their water solubility depends on polarity.
Giant ionic compounds like sodium chloride behave totally differently. They're solid at room temperature with high melting points because you need massive energy to break strong electrostatic forces between ions. They conduct when liquid because ions can move freely.
Moving on to electron configuration - this might seem tricky, but it's just about filling electron "parking spaces" in order. The s subshell holds 2 electrons, p holds 6, d holds 10, and f holds 14. Remember that electrons prefer to occupy empty orbitals first before pairing up.
For ions, simply add or remove electrons from the highest energy level. Calcium (Ca) has 20 electrons, but Ca²⁺ has lost 2 electrons, giving it 18. Use noble gas notation like [Ar] 4s¹ for potassium to save time in exams.
Memory Trick: Higher shell numbers mean electrons are further from the nucleus and have higher energy levels.
3
of 4Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Orbital Shapes
Orbitals aren't just abstract concepts - they're actual 3D regions where electrons hang out around the nucleus. Understanding their shapes helps explain how atoms bond and behave.
S orbitals are perfectly spherical, whilst p orbitals are dumbbell-shaped and come in three orientations (px, py, pz). When filling orbitals, electrons spin in opposite directions to minimise repulsion - think of it like they're trying to avoid each other!
The aufbau principle is your roadmap for electron configuration. Fill lower energy levels first, and remember that 4s fills before 3d (even though 3d is written first in the final configuration). For iron (Fe), you get: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s².
When atoms form ions, they lose or gain electrons to achieve stable configurations. This is fundamental to understanding chemical reactivity and bonding patterns you'll encounter throughout A-level chemistry.
Exam Success: Always check your electron numbers add up to the atomic number for neutral atoms!
4
of 4Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Acids and Bases
Acids are proton donors and bases are proton acceptors - this Brønsted-Lowry definition is absolutely essential for A-level success. When acids and bases react, they're essentially swapping protons (H⁺ ions).
Strong acids like HCl, H₂SO₄, and HNO₃ completely dissociate in water, flooding the solution with H⁺ ions. Weak acids like ethanoic acid only partially dissociate, creating an equilibrium. The same principle applies to strong bases (NaOH, KOH) versus weak bases (NH₃).
Neutralisation reactions always follow the same pattern: acid + base → salt + water. The key reaction is H⁺ + OH⁻ → H₂O. You'll also need to know that metals react with acids to produce hydrogen gas, whilst metal carbonates produce carbon dioxide.
Polyprotic acids can donate multiple protons - monoprotic (like HNO₃), diprotic (like H₂SO₄), or triprotic (like H₃PO₄). This affects stoichiometry in calculations, so always check how many protons each acid can donate.
Equation Mastery: Learn the ionic equations - they show what's actually happening chemically and often earn extra marks in exams.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar content
Most popular content: Hydrogen Bonding
4ChemistryStructure & Bonding Overview
Explore the key concepts of metallic, ionic, and covalent bonding, including their structures, properties, and the effects of intermolecular forces. This summary covers the principles of bonding types, crystal structures, and the VSEPR theory, providing essential insights for AQA A Level Chemistry students. Ideal for exam preparation and understanding material properties.
1239216
ChemistryUnderstanding Intermolecular Forces
Explore the key concepts of intermolecular forces, including dipole-dipole interactions, hydrogen bonding, and Van der Waals forces. This summary provides insights into how these forces influence molecular shape, boiling points, and physical properties of substances. Ideal for students studying chemistry and looking to grasp the fundamentals of molecular interactions.
131693
ChemistryElectronegativity & Intermolecular Forces
Explore the concepts of electronegativity, dipole moments, and intermolecular forces including hydrogen bonding and van der Waals forces. This summary covers the nature of polar and non-polar bonds, the significance of dipole-dipole interactions, and how these factors influence the physical properties of substances. Ideal for AQA A Level & AS Chemistry students.
1219815
ChemistryUnderstanding Intermolecular Forces
Explore the key types of intermolecular forces, including London dispersion forces, dipole-dipole interactions, and hydrogen bonding. This summary highlights their mechanisms, strengths, and effects on physical properties like boiling points, tailored for AQA A-level Chemistry students.
1219410
Most popular content in Chemistry
9G
ChemistryGCSE AQA Chemistry Topic 1- The Atom
The Atom
109270
Chemistrychem paper 1
higher
111,79537
G
ChemistryGCSE AQA Chemistry Topic 1
Quiz covering all of topic 1
101,6583
ChemistryA-level OCR A Chemistry summary sheets
Everything from snaprevise for OCR chemistry a-level
121,99677
ChemistryEssential Chemistry Practicals
Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.
1011,775902
C
Chemistrychem paper 1
Unlock the secrets of chemical reactions with this comprehensive flashcard set designed to help you conquer complex concepts and ace your Chemistry exams.
115861
A
ChemistryAQA GCSE Chemistry 4.2 Bonding, structure and the Properties of Matter
4.2 Metals and Alloys
96740
A
ChemistryAQA GCSE Chemistry 4.4 Chemical changes
4.4 Reactions of acids with bases or carbonates
95521
F
ChemistryFundamentals of Atomic Structure
Practice identifying subatomic particles, calculating neutrons, and defining isotopes and atomic/mass numbers.
123400
Most popular content
9SociologySociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
12101,9513,036
SociologySociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
1271,5982,281
English LiteratureAn Inspector Calls: Character Insights
Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.
1025,049896
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1251,7131,025
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
126,396118
CriminologyCriminology Theories Overview
Explore key criminology theories and their implications on crime and deviance. This comprehensive summary covers biological, psychological, and sociological perspectives, including labelling theory, right realism, and the impact of social campaigns on policy development. Ideal for A-Level criminology students seeking to understand the complexities of criminal behaviour and the factors influencing crime prevention strategies.
129,732211
English LiteratureRomeo and Juliet: Key themes
Key Romeo and Juliet themes and analysed quotes
106,561193
English LiteratureMacbeth: Guilt and Ambition
Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.
918,657387
BiologyAQA Biology: Key Concepts
Explore essential AQA Biology topics including Photosynthesis, Respiration, Homeostasis, Genetics, and Ecology. This comprehensive knowledge organizer covers key concepts such as energy transfer, hormonal control, and genetic variation, providing a solid foundation for your studies. Ideal for exam preparation and understanding biological processes.
108,325295
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user