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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
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Inter-war germany
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2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
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Chemistry
13 Dec 2025
557
2 pages
Ever wondered how atoms stick together to form the substances around you? Covalent bonding is nature's way of... Show more
Covalent bonding happens when two non-metal atoms decide to share electrons rather than give them away completely. Think of it like sharing a favourite book with a mate - both of you get to use it!
The simplest example is hydrogen gas (Hโ). Two hydrogen atoms each contribute one electron to form a shared pair, creating what we call a single covalent bond. This sharing helps both atoms achieve a full outer energy level, making them much happier and more stable.
You can represent these bonds in three different ways dot and cross diagrams (showing individual electrons), energy level diagrams (showing electron shells), and stick diagrams (where each line represents a shared pair). The stick diagram H-H is probably the easiest to draw in exams!
Key Point In hydrogen chloride (HCl), hydrogen shares its single electron with chlorine, whilst chlorine shares one of its seven outer electrons back - perfect teamwork for a stable molecule.
Not all atoms are satisfied with just one shared pair! Oxygen molecules (Oโ) form double covalent bonds by sharing two pairs of electrons, shown as O=O. Nitrogen (Nโ) goes even further with a triple bond (NโกN), sharing three pairs - making it incredibly strong and stable.
Small covalent molecules like water, ammonia, and methane have surprisingly low melting and boiling points. Most are gases or liquids at room temperature, which explains why you can breathe oxygen and why water flows from your tap.
Here's the clever bit whilst the covalent bonds within each molecule are incredibly strong, the intermolecular forces between different molecules are really weak. It's like having super-strong friendship groups, but the groups barely interact with each other.
Remember Dot and cross diagrams have limitations - they're 2D representations that don't show actual atomic sizes, so don't expect molecules to look exactly like your drawings in real life!
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help โ all at your fingertips.
7
Smart Tools NEW
Transform this note into: โ 50+ Practice Questions โ Interactive Flashcards โ Full Mock Exam โ Essay Outlines
Explore the fundamentals of ion formation in chemistry, focusing on the role of protons, electrons, and neutrons. This summary covers key concepts such as isotopes, electron configuration in the periodic table, and the behavior of different groups in forming ions. Ideal for Year 9 students studying ionic bonding and chemical ions.
ChemistryExplore key concepts in atomic structure, the periodic table, and the properties of matter. This comprehensive revision note covers atomic models, chemical bonding (ionic, covalent, and metallic), and the characteristics of elements in groups such as alkali metals and noble gases. Ideal for GCSE students preparing for exams.
ChemistryExplore essential GCSE Chemistry concepts including atomic structure, chemical bonding, redox reactions, and electrolysis. This comprehensive mind map is designed for Grade 9 students preparing for the OCR exam board, covering key topics such as ionic and covalent compounds, oxidation, and neutralization reactions.
ChemistryExplore the fundamental concepts of elements and atoms, including definitions, properties, and common chemical symbols. This summary covers key terms such as chemical, molecule, formula, polymer, and compound, essential for Year 8 science students.
ChemistryExplore the fundamental concepts of chemistry with this concise summary on mixtures, elements, and compounds. Learn about key separation methods such as filtration, crystallisation, fractional distillation, and chromatography. Ideal for GCSE chemistry students seeking to grasp essential definitions and processes related to atoms and substances.
ChemistryExplore essential chemistry topics including electrolysis, balancing equations, types of chemical reactions, and the law of conservation of mass. This summary covers atomic structure, acid-base reactions, and combustion processes, providing a comprehensive overview for Year 7-8 students.
ChemistryApp Store
Google 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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because itโs too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH ๐๐๐ฒ๐ค๐โจ๐๐ฎ
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because itโs too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH ๐๐๐ฒ๐ค๐โจ๐๐ฎ
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Ever wondered how atoms stick together to form the substances around you? Covalent bonding is nature's way of letting non-metal atoms share electrons to create everything from the water you drink to the air you breathe.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Covalent bonding happens when two non-metal atoms decide to share electrons rather than give them away completely. Think of it like sharing a favourite book with a mate - both of you get to use it!
The simplest example is hydrogen gas (Hโ). Two hydrogen atoms each contribute one electron to form a shared pair, creating what we call a single covalent bond. This sharing helps both atoms achieve a full outer energy level, making them much happier and more stable.
You can represent these bonds in three different ways: dot and cross diagrams (showing individual electrons), energy level diagrams (showing electron shells), and stick diagrams (where each line represents a shared pair). The stick diagram H-H is probably the easiest to draw in exams!
Key Point: In hydrogen chloride (HCl), hydrogen shares its single electron with chlorine, whilst chlorine shares one of its seven outer electrons back - perfect teamwork for a stable molecule.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Not all atoms are satisfied with just one shared pair! Oxygen molecules (Oโ) form double covalent bonds by sharing two pairs of electrons, shown as O=O. Nitrogen (Nโ) goes even further with a triple bond (NโกN), sharing three pairs - making it incredibly strong and stable.
Small covalent molecules like water, ammonia, and methane have surprisingly low melting and boiling points. Most are gases or liquids at room temperature, which explains why you can breathe oxygen and why water flows from your tap.
Here's the clever bit: whilst the covalent bonds within each molecule are incredibly strong, the intermolecular forces between different molecules are really weak. It's like having super-strong friendship groups, but the groups barely interact with each other.
Remember: Dot and cross diagrams have limitations - they're 2D representations that don't show actual atomic sizes, so don't expect molecules to look exactly like your drawings in real life!
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help โ all at your fingertips.
7
Smart Tools NEW
Transform this note into: โ 50+ Practice Questions โ Interactive Flashcards โ Full Mock Exam โ Essay Outlines
Explore the fundamentals of ion formation in chemistry, focusing on the role of protons, electrons, and neutrons. This summary covers key concepts such as isotopes, electron configuration in the periodic table, and the behavior of different groups in forming ions. Ideal for Year 9 students studying ionic bonding and chemical ions.
ChemistryExplore key concepts in atomic structure, the periodic table, and the properties of matter. This comprehensive revision note covers atomic models, chemical bonding (ionic, covalent, and metallic), and the characteristics of elements in groups such as alkali metals and noble gases. Ideal for GCSE students preparing for exams.
ChemistryExplore essential GCSE Chemistry concepts including atomic structure, chemical bonding, redox reactions, and electrolysis. This comprehensive mind map is designed for Grade 9 students preparing for the OCR exam board, covering key topics such as ionic and covalent compounds, oxidation, and neutralization reactions.
ChemistryExplore the fundamental concepts of elements and atoms, including definitions, properties, and common chemical symbols. This summary covers key terms such as chemical, molecule, formula, polymer, and compound, essential for Year 8 science students.
ChemistryExplore the fundamental concepts of chemistry with this concise summary on mixtures, elements, and compounds. Learn about key separation methods such as filtration, crystallisation, fractional distillation, and chromatography. Ideal for GCSE chemistry students seeking to grasp essential definitions and processes related to atoms and substances.
ChemistryExplore essential chemistry topics including electrolysis, balancing equations, types of chemical reactions, and the law of conservation of mass. This summary covers atomic structure, acid-base reactions, and combustion processes, providing a comprehensive overview for Year 7-8 students.
ChemistryApp Store
Google 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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because itโs too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH ๐๐๐ฒ๐ค๐โจ๐๐ฎ
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because itโs too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH ๐๐๐ฒ๐ค๐โจ๐๐ฎ
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Sociology