Maths
Chemistry
Biology
English Language
History
Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
Medieval period: 1066 -1509
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
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
World war one
Britain: 1509 -1745
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7 Dec 2025
•
Ffion Johnson
@theylove.ffion
Ever wondered why metals conduct electricity whilst plastic doesn't? It's... Show more
Think of metals as having a "sea of electrons" that's free to move around. When metal atoms bond together, they form giant structures with regularly arranged atoms, but here's the clever bit - the electrons from their outer shells become delocalised, meaning they're no longer tied to specific atoms.
This sharing of delocalised electrons creates strong metallic bonds. The strength comes from the attraction between the positively charged metal ions and the negatively charged delocalised electrons moving freely through the structure.
These free electrons are the reason metals have their unique properties. They conduct electricity because the delocalised electrons carry electrical charge, and they conduct heat as these electrons transfer energy efficiently through the closely packed structure.
Quick tip: Remember that metallic bonding only happens between metal atoms - it's what gives metals their "metallic" properties!
Metals are also malleable and ductile (you can hammer and stretch them) because the layers of metal ions can slide over each other when force is applied. Plus, they have high melting and boiling points since you need loads of energy to break those strong metallic bonds.
Here's something that'll help you predict properties across the periodic table. As you move across any period, metals get higher melting and boiling points.
This happens because there are more delocalised electrons available as you go across a period. More delocalised electrons means stronger attraction between the ions and free electrons, which creates stronger bonds overall.
Exam tip: This trend question comes up regularly - just remember more electrons equals stronger bonds!
It's a straightforward pattern once you get it, and it explains why some metals are much harder to melt than others.
Ionic bonding happens when metals meet non-metals, and it's basically an electron transfer situation. Metal atoms lose electrons to become positive ions, whilst non-metal atoms gain those electrons to become negative ions.
The key idea is that both atoms are trying to achieve full outer shells. Metals happily give up electrons (they've got few in their outer shell anyway), and non-metals readily accept them (they're nearly full already).
You'll need to draw dot and cross diagrams to show this electron transfer. Take sodium chloride - sodium (2,8,1) gives its outer electron to chlorine (2,8,7), creating Na⁺ and Cl⁻ ions.
Memory trick: Metals GIVE electrons (they're generous!), non-metals TAKE electrons (they're greedy!).
For compounds like lithium oxide, you need two lithium atoms to give up one electron each to fill oxygen's outer shell, since oxygen needs two electrons to complete its shell.
Covalent bonding is completely different from ionic bonding - instead of transferring electrons, atoms share electrons to achieve full outer shells. This only happens between non-metal atoms.
Single bonds involve sharing one pair of electrons. Water (H₂O) is a perfect example - the oxygen atom shares electrons with two hydrogen atoms, giving everyone a full outer shell.
You'll also encounter double bonds where two pairs of electrons are shared. Oxygen gas (O₂) and carbon dioxide (CO₂) are classic examples of this.
Quick check: If it's metal + non-metal = ionic bonding. If it's non-metal + non-metal = covalent bonding!
The dot and cross diagrams for covalent bonding show the shared electron pairs between atoms, rather than the complete electron transfer you see in ionic bonding.
Giant ionic structures form when ionic compounds arrange themselves into regular patterns called ionic lattices. The oppositely charged ions attract each other in a repeating 3D arrangement that maximises attraction and minimises repulsion.
These structures have high melting and boiling points because of the strong electrostatic forces between ions. They only conduct electricity when molten or dissolved - that's when the ions are free to move and carry charge.
Simple molecular structures are completely different beasts. These are small molecules like hydrogen, water, and carbon dioxide held together by strong covalent bonds within each molecule, but only weak forces between different molecules.
Key insight: It's the weak forces BETWEEN molecules that determine the properties, not the strong bonds WITHIN molecules!
This explains why simple molecular compounds have low melting and boiling points - you're only breaking the weak intermolecular forces, not the strong covalent bonds. They also don't conduct electricity since there are no free electrons or ions.
Giant covalent structures are like simple molecules on steroids - thousands of atoms held together by covalent bonds in massive lattices. The sheer number of bonds makes these structures incredibly strong.
Diamond has each carbon atom bonded to four others in a 3D network. It doesn't conduct electricity (no delocalised electrons) but it's brilliant for drill bits and glass cutting because of its extreme hardness.
Graphite is more interesting - each carbon bonds to only three others, creating layers. It conducts electricity because of delocalised electrons between the layers, and the layers can slide over each other, making it perfect for pencils and lubricants.
Exam favourite: You'll definitely get asked about diamond vs graphite properties - remember the bonding pattern determines everything!
The key difference between diamond and graphite shows how the same element can have completely different properties based on how the atoms are arranged and bonded.
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 – all at your fingertips.
Quotes from every main character
English LiteratureApp 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 it’s 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 didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m 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 😍😁😲🤑💗✨🎀😮
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 it’s 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 didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m 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 😍😁😲🤑💗✨🎀😮
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
Ffion Johnson
@theylove.ffion
Ever wondered why metals conduct electricity whilst plastic doesn't? It's all down to the different ways atoms bond together. Understanding metallic, ionic, and covalent bonding explains pretty much every material property you encounter daily.
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Think of metals as having a "sea of electrons" that's free to move around. When metal atoms bond together, they form giant structures with regularly arranged atoms, but here's the clever bit - the electrons from their outer shells become delocalised, meaning they're no longer tied to specific atoms.
This sharing of delocalised electrons creates strong metallic bonds. The strength comes from the attraction between the positively charged metal ions and the negatively charged delocalised electrons moving freely through the structure.
These free electrons are the reason metals have their unique properties. They conduct electricity because the delocalised electrons carry electrical charge, and they conduct heat as these electrons transfer energy efficiently through the closely packed structure.
Quick tip: Remember that metallic bonding only happens between metal atoms - it's what gives metals their "metallic" properties!
Metals are also malleable and ductile (you can hammer and stretch them) because the layers of metal ions can slide over each other when force is applied. Plus, they have high melting and boiling points since you need loads of energy to break those strong metallic bonds.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's something that'll help you predict properties across the periodic table. As you move across any period, metals get higher melting and boiling points.
This happens because there are more delocalised electrons available as you go across a period. More delocalised electrons means stronger attraction between the ions and free electrons, which creates stronger bonds overall.
Exam tip: This trend question comes up regularly - just remember more electrons equals stronger bonds!
It's a straightforward pattern once you get it, and it explains why some metals are much harder to melt than others.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ionic bonding happens when metals meet non-metals, and it's basically an electron transfer situation. Metal atoms lose electrons to become positive ions, whilst non-metal atoms gain those electrons to become negative ions.
The key idea is that both atoms are trying to achieve full outer shells. Metals happily give up electrons (they've got few in their outer shell anyway), and non-metals readily accept them (they're nearly full already).
You'll need to draw dot and cross diagrams to show this electron transfer. Take sodium chloride - sodium (2,8,1) gives its outer electron to chlorine (2,8,7), creating Na⁺ and Cl⁻ ions.
Memory trick: Metals GIVE electrons (they're generous!), non-metals TAKE electrons (they're greedy!).
For compounds like lithium oxide, you need two lithium atoms to give up one electron each to fill oxygen's outer shell, since oxygen needs two electrons to complete its shell.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Covalent bonding is completely different from ionic bonding - instead of transferring electrons, atoms share electrons to achieve full outer shells. This only happens between non-metal atoms.
Single bonds involve sharing one pair of electrons. Water (H₂O) is a perfect example - the oxygen atom shares electrons with two hydrogen atoms, giving everyone a full outer shell.
You'll also encounter double bonds where two pairs of electrons are shared. Oxygen gas (O₂) and carbon dioxide (CO₂) are classic examples of this.
Quick check: If it's metal + non-metal = ionic bonding. If it's non-metal + non-metal = covalent bonding!
The dot and cross diagrams for covalent bonding show the shared electron pairs between atoms, rather than the complete electron transfer you see in ionic bonding.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Giant ionic structures form when ionic compounds arrange themselves into regular patterns called ionic lattices. The oppositely charged ions attract each other in a repeating 3D arrangement that maximises attraction and minimises repulsion.
These structures have high melting and boiling points because of the strong electrostatic forces between ions. They only conduct electricity when molten or dissolved - that's when the ions are free to move and carry charge.
Simple molecular structures are completely different beasts. These are small molecules like hydrogen, water, and carbon dioxide held together by strong covalent bonds within each molecule, but only weak forces between different molecules.
Key insight: It's the weak forces BETWEEN molecules that determine the properties, not the strong bonds WITHIN molecules!
This explains why simple molecular compounds have low melting and boiling points - you're only breaking the weak intermolecular forces, not the strong covalent bonds. They also don't conduct electricity since there are no free electrons or ions.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Giant covalent structures are like simple molecules on steroids - thousands of atoms held together by covalent bonds in massive lattices. The sheer number of bonds makes these structures incredibly strong.
Diamond has each carbon atom bonded to four others in a 3D network. It doesn't conduct electricity (no delocalised electrons) but it's brilliant for drill bits and glass cutting because of its extreme hardness.
Graphite is more interesting - each carbon bonds to only three others, creating layers. It conducts electricity because of delocalised electrons between the layers, and the layers can slide over each other, making it perfect for pencils and lubricants.
Exam favourite: You'll definitely get asked about diamond vs graphite properties - remember the bonding pattern determines everything!
The key difference between diamond and graphite shows how the same element can have completely different properties based on how the atoms are arranged and bonded.
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 – all at your fingertips.
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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Quotes from every main character
English LiteratureApp 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 it’s 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 didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m 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 😍😁😲🤑💗✨🎀😮
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 it’s 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 didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m 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 😍😁😲🤑💗✨🎀😮
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