Subjects
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
Show all topics
1l the quest for political stability: germany, 1871-1991
Britain & the wider world: 1745 -1901
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
Show all topics
Biology
27 Nov 2025
76
4 pages
AbigailTheFish @fishythefish
Everything around you - from your phone to the air you breathe - is made of tiny building... Show more
Matter is literally everything you can touch, smell, taste or feel - basically anything that has mass or takes up space. At the heart of all matter are atoms, which are so incredibly small you can't see them even with the most powerful school microscopes.
Think of atoms like invisible LEGO blocks that make up everything. Each atom has three main parts protons (positive charge), neutrons (no charge), and electrons (negative charge). The protons and neutrons huddle together in the centre called the nucleus, whilst electrons zip around the outside.
Here's something cool atoms are basically lazy! They absorb energy from heat, light and sound, then vibrate and release that energy because they prefer to chill out with as little energy as possible. The less energy they have, the more stable they become.
Quick Fact Scientists have discovered 118 different types of atoms in nature, and each type is called an element!
The periodic table is like a massive organised grid where all 118 elements have their own special spot. Each element gets positioned based on its atomic number - which is simply the number of protons it has.
Every square on the periodic table tells you loads about that element its chemical symbol (like Mg for magnesium), atomic number, element name, and atomic mass. The table is arranged in horizontal periods and vertical groups, with elements lined up from left to right by increasing atomic number.
Electrons don't just randomly float around the nucleus - they travel in organised rings called electron shells. The electrons closest to the nucleus are called core electrons and are super stable with low energy. The ones furthest out are valence electrons - these are the troublemakers with high energy who are more likely to break away.
Remember As you move across the periodic table from left to right, each element has exactly one more proton and electron than the element before it!
Understanding how electrons fill up their shells is dead important! The first shell holds 2 electrons, the second holds 8, the third holds 8, and the fourth holds 2. When shells aren't completely filled, atoms get a bit restless and want to bond with other atoms to become more stable.
Covalent bonding is when atoms become best mates by sharing pairs of electrons. This sharing fills up their outermost energy levels, making them happy and stable. When atoms bond together, they form molecules. If that molecule contains two or more different elements, it's called a compound.
Think of it like this atoms with incomplete outer shells are like puzzles missing pieces. The positive charge from the nucleus creates attractive forces that pull in nearby electrons to fill those gaps, completing the puzzle and lowering the atom's energy.
Key Point Atoms bond because they're trying to reach their lowest energy state - it's all about finding stability!
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
Explore the fundamental concepts of elements, isotopes, and relative atomic mass in this detailed summary. Learn how isotopes differ, the significance of atomic mass units (amu), and how to calculate the relative atomic mass using real examples like chlorine. Ideal for chemistry students seeking clarity on these essential topics.
ChemistryExplore the fundamental concepts of atoms, ions, isotopes, and their properties. This summary covers atomic structure, the formation of ions, the distinction between elements, compounds, and mixtures, and the historical development of atomic theory. Ideal for GCSE Chemistry students.
ChemistryExplore the fundamentals of atomic structure, including subatomic particles, atomic mass, and the distinction between elements, compounds, and mixtures. This summary covers key concepts such as protons, neutrons, electrons, and how they form molecules and compounds. Ideal for students studying chemistry.
ChemistryExplore the fundamental concepts of atomic structure and ion formation in this GCSE chemistry summary. Learn about protons, neutrons, electrons, and how atoms become ions through the loss or gain of electrons. Ideal for students seeking clarity on cations and the balance of charges within atoms.
ChemistryExplore the fundamentals of atomic structure and bonding, including atomic numbers, mass numbers, ionic and covalent bonds, and the periodic table. This summary covers key concepts essential for understanding chemical properties and compound formation. Ideal for chemistry students preparing for exams.
ChemistryExplore the fundamentals of atomic structure, including subatomic particles, elements, and compounds. Learn techniques for separating mixtures such as filtration, crystallization, and distillation. This summary covers key concepts in atomic theory and the development of the atomic model, ideal for students preparing for exams.
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 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
AbigailTheFish
@fishythefish
Everything around you - from your phone to the air you breathe - is made of tiny building blocks called atoms. Understanding atoms and how they stick together to form molecules is like having the secret code to understand all... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Matter is literally everything you can touch, smell, taste or feel - basically anything that has mass or takes up space. At the heart of all matter are atoms, which are so incredibly small you can't see them even with the most powerful school microscopes.
Think of atoms like invisible LEGO blocks that make up everything. Each atom has three main parts: protons (positive charge), neutrons (no charge), and electrons (negative charge). The protons and neutrons huddle together in the centre called the nucleus, whilst electrons zip around the outside.
Here's something cool: atoms are basically lazy! They absorb energy from heat, light and sound, then vibrate and release that energy because they prefer to chill out with as little energy as possible. The less energy they have, the more stable they become.
Quick Fact: Scientists have discovered 118 different types of atoms in nature, and each type is called an element!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The periodic table is like a massive organised grid where all 118 elements have their own special spot. Each element gets positioned based on its atomic number - which is simply the number of protons it has.
Every square on the periodic table tells you loads about that element: its chemical symbol (like Mg for magnesium), atomic number, element name, and atomic mass. The table is arranged in horizontal periods and vertical groups, with elements lined up from left to right by increasing atomic number.
Electrons don't just randomly float around the nucleus - they travel in organised rings called electron shells. The electrons closest to the nucleus are called core electrons and are super stable with low energy. The ones furthest out are valence electrons - these are the troublemakers with high energy who are more likely to break away.
Remember: As you move across the periodic table from left to right, each element has exactly one more proton and electron than the element before it!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Understanding how electrons fill up their shells is dead important! The first shell holds 2 electrons, the second holds 8, the third holds 8, and the fourth holds 2. When shells aren't completely filled, atoms get a bit restless and want to bond with other atoms to become more stable.
Covalent bonding is when atoms become best mates by sharing pairs of electrons. This sharing fills up their outermost energy levels, making them happy and stable. When atoms bond together, they form molecules. If that molecule contains two or more different elements, it's called a compound.
Think of it like this: atoms with incomplete outer shells are like puzzles missing pieces. The positive charge from the nucleus creates attractive forces that pull in nearby electrons to fill those gaps, completing the puzzle and lowering the atom's energy.
Key Point: Atoms bond because they're trying to reach their lowest energy state - it's all about finding stability!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
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.
2
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the fundamental concepts of elements, isotopes, and relative atomic mass in this detailed summary. Learn how isotopes differ, the significance of atomic mass units (amu), and how to calculate the relative atomic mass using real examples like chlorine. Ideal for chemistry students seeking clarity on these essential topics.
ChemistryExplore the fundamental concepts of atoms, ions, isotopes, and their properties. This summary covers atomic structure, the formation of ions, the distinction between elements, compounds, and mixtures, and the historical development of atomic theory. Ideal for GCSE Chemistry students.
ChemistryExplore the fundamentals of atomic structure, including subatomic particles, atomic mass, and the distinction between elements, compounds, and mixtures. This summary covers key concepts such as protons, neutrons, electrons, and how they form molecules and compounds. Ideal for students studying chemistry.
ChemistryExplore the fundamental concepts of atomic structure and ion formation in this GCSE chemistry summary. Learn about protons, neutrons, electrons, and how atoms become ions through the loss or gain of electrons. Ideal for students seeking clarity on cations and the balance of charges within atoms.
ChemistryExplore the fundamentals of atomic structure and bonding, including atomic numbers, mass numbers, ionic and covalent bonds, and the periodic table. This summary covers key concepts essential for understanding chemical properties and compound formation. Ideal for chemistry students preparing for exams.
ChemistryExplore the fundamentals of atomic structure, including subatomic particles, elements, and compounds. Learn techniques for separating mixtures such as filtration, crystallization, and distillation. This summary covers key concepts in atomic theory and the development of the atomic model, ideal for students preparing for exams.
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 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
