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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
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2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
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Chemistry
1 Dec 2025
529
1 page
hamna ๐ @breaddstick
Atoms are the building blocks of everything around you, from your phone to the air you breathe. Understanding... Show more
Atoms are incredibly small and dense particles with a relative mass of just 1/2000th compared to everyday objects. Each atom contains a nucleus (made of protons and neutrons) surrounded by electrons in shells.
An element is simply a substance made entirely of one type of atom - think of pure gold or pure oxygen. Isotopes are atoms of the same element that have different numbers of neutrons, but they behave identically in chemical reactions because electrons control reactivity.
When atoms gain or lose electrons, they become ions - charged particles. Cations are positively charged (lost electrons) whilst anions are negatively charged (gained electrons).
Key Point Isotopes don't affect chemical behaviour because electrons, not neutrons, determine how atoms react.
Scientists measure atomic mass using relative isotopic mass - comparing each isotope to 1/12th of a carbon-12 atom (called 1u, roughly equal to one proton or neutron). Relative atomic mass is the weighted average of all isotopes of an element.
Mass spectrometers help us find percentage abundance of isotopes. The sample gets vaporised and ionised (made positive), then ions are accelerated and separated by mass - heavier ions move slower through the drift region.
You can calculate relative atomic mass using relative atomic mass = ฮฃ(percentage abundance ร relative isotopic mass) รท ฮฃ percentage abundance. Notice there are no units and it's rarely a whole number.
Key Point Mass spectrometers separate ions by mass because heavier particles travel slower when accelerated to the same speed.
Simple ions form when single atoms lose or gain electrons. Groups 1, 2, and 3 typically lose electrons , whilst groups 5, 6, and 7 gain electrons . Negative ions end in -ide.
Key exceptions to remember hydrogen can form hydride ion (Hโป), zinc forms Znยฒโบ, silver forms Agโบ, and scandium forms Scยณโบ.
Polyatomic ions are groups of different atoms that gain or lose electrons together. Essential ones include ammonium (NHโโบ), nitrate (NOโโป), carbonate (COโยฒโป), sulfate (SOโยฒโป), and phosphate (POโยณโป).
Key Point Group numbers often predict ion charges - Group 1 forms 1+ ions, Group 2 forms 2+ ions, and so on.
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.
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Explore the concepts of atom economy, percentage yield, and the significance of hydrated vs. anhydrous salts in A-level Physical Chemistry. This summary covers key calculations, the ideal gas equation, and the importance of efficient chemical reactions for sustainability. Ideal for students preparing for exams.
ChemistryExplore the fundamentals of atomic structure, including ionization energies, electron configurations, isotopes, and mass spectrometry. This comprehensive summary covers key concepts such as atomic radius, shielding effects, and the historical development of atomic models. Ideal for A-level Chemistry students preparing for exams.
ChemistryExplore the principles and methods of mass spectrometry, including electron impact and electrospray ionisation. Understand how molecular ions are formed, the significance of mass spectra, and how to calculate relative atomic mass. Ideal for AQA A-level chemistry students.
ChemistryC1 Chemistry (Atoms etc)
ChemistryExplore the fundamentals of isotopes, including definitions, calculations of relative atomic mass, and the relationship between protons, neutrons, and mass number. This summary covers key concepts such as relative abundance and atomic structure, essential for mastering Module 2 in Chemistry.
ChemistryExplore the concepts of mass number, atomic number, and isotopes in this detailed summary for A Level Chemistry. Learn how to calculate relative atomic mass, understand the significance of ions, and differentiate between isotopes. This resource includes examples and calculations to enhance your understanding of atomic structure.
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
hamna ๐
@breaddstick
Atoms are the building blocks of everything around you, from your phone to the air you breathe. Understanding how atoms work, how we measure them, and how they form ions is crucial for mastering chemistry at A-level.
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Atoms are incredibly small and dense particles with a relative mass of just 1/2000th compared to everyday objects. Each atom contains a nucleus (made of protons and neutrons) surrounded by electrons in shells.
An element is simply a substance made entirely of one type of atom - think of pure gold or pure oxygen. Isotopes are atoms of the same element that have different numbers of neutrons, but they behave identically in chemical reactions because electrons control reactivity.
When atoms gain or lose electrons, they become ions - charged particles. Cations are positively charged (lost electrons) whilst anions are negatively charged (gained electrons).
Key Point: Isotopes don't affect chemical behaviour because electrons, not neutrons, determine how atoms react.
Scientists measure atomic mass using relative isotopic mass - comparing each isotope to 1/12th of a carbon-12 atom (called 1u, roughly equal to one proton or neutron). Relative atomic mass is the weighted average of all isotopes of an element.
Mass spectrometers help us find percentage abundance of isotopes. The sample gets vaporised and ionised (made positive), then ions are accelerated and separated by mass - heavier ions move slower through the drift region.
You can calculate relative atomic mass using: relative atomic mass = ฮฃ(percentage abundance ร relative isotopic mass) รท ฮฃ percentage abundance. Notice there are no units and it's rarely a whole number.
Key Point: Mass spectrometers separate ions by mass because heavier particles travel slower when accelerated to the same speed.
Simple ions form when single atoms lose or gain electrons. Groups 1, 2, and 3 typically lose electrons , whilst groups 5, 6, and 7 gain electrons . Negative ions end in -ide.
Key exceptions to remember: hydrogen can form hydride ion (Hโป), zinc forms Znยฒโบ, silver forms Agโบ, and scandium forms Scยณโบ.
Polyatomic ions are groups of different atoms that gain or lose electrons together. Essential ones include ammonium (NHโโบ), nitrate (NOโโป), carbonate (COโยฒโป), sulfate (SOโยฒโป), and phosphate (POโยณโป).
Key Point: Group numbers often predict ion charges - Group 1 forms 1+ ions, Group 2 forms 2+ ions, and so on.
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.
0
Smart Tools NEW
Transform this note into: โ 50+ Practice Questions โ Interactive Flashcards โ Full Mock Exam โ Essay Outlines
Explore the concepts of atom economy, percentage yield, and the significance of hydrated vs. anhydrous salts in A-level Physical Chemistry. This summary covers key calculations, the ideal gas equation, and the importance of efficient chemical reactions for sustainability. Ideal for students preparing for exams.
ChemistryExplore the fundamentals of atomic structure, including ionization energies, electron configurations, isotopes, and mass spectrometry. This comprehensive summary covers key concepts such as atomic radius, shielding effects, and the historical development of atomic models. Ideal for A-level Chemistry students preparing for exams.
ChemistryExplore the principles and methods of mass spectrometry, including electron impact and electrospray ionisation. Understand how molecular ions are formed, the significance of mass spectra, and how to calculate relative atomic mass. Ideal for AQA A-level chemistry students.
ChemistryC1 Chemistry (Atoms etc)
ChemistryExplore the fundamentals of isotopes, including definitions, calculations of relative atomic mass, and the relationship between protons, neutrons, and mass number. This summary covers key concepts such as relative abundance and atomic structure, essential for mastering Module 2 in Chemistry.
ChemistryExplore the concepts of mass number, atomic number, and isotopes in this detailed summary for A Level Chemistry. Learn how to calculate relative atomic mass, understand the significance of ions, and differentiate between isotopes. This resource includes examples and calculations to enhance your understanding of atomic structure.
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