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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
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Chemistry
8 Dec 2025
452
2 pages
Understanding where electrons live around an atom's nucleus isn't as simple as GCSE chemistry suggested. At A-level, you'll... Show more
Remember from GCSE that electrons exist in electron shells around the nucleus? Well, scientists give each shell a number called the principal quantum number, written as "n". The first shell is n=1, the second is n=2, and so on.
Here's the brilliant bit you can calculate the maximum number of electrons any shell can hold using the formula 2n². So shell 1 holds 2×1² = 2 electrons, shell 2 holds 2×2² = 8 electrons, shell 3 holds 18, and shell 4 holds 32 electrons.
But here's where it gets interesting - electrons aren't just floating around randomly in these shells. They occupy specific regions called atomic orbitals. Think of an atomic orbital as a 3D space around the nucleus where you're likely to find up to two electrons.
Key Point Each orbital can hold a maximum of two electrons, but they must have opposite spins - one "up" and one "down".
The electrons behave like clouds of negative charge, and these clouds take on the actual shape of the orbital they're occupying. There are four main types of orbitals, each with its own letter s, p, d, and f.
S orbitals are the simplest - they're perfectly spherical, like a ball around the nucleus. Every single electron shell contains exactly one s orbital.
P orbitals look completely different - they're shaped like dumbbells or figure-8s. There are always three p orbitals in each shell, except for the first shell which doesn't have any p orbitals at all.
D orbitals are more complex, with five different d orbitals appearing in shell 3 and above. F orbitals are the most complicated, with seven different f orbitals that only show up in shell 4 and higher.
Remember A subshell is just all the orbitals of the same type in one shell - like "2p" (all three p orbitals in shell 2) or "3d" (all five d orbitals in shell 3).
This explains why electron capacity jumps so dramatically as you move outward from the nucleus. Shell 1 only has an s orbital (2 electrons max), but shell 4 has s, p, d, and f orbitals, giving it space for 32 electrons total.
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Explore advanced concepts in chemical equilibrium, including equilibrium constants (Kc and Kp), the effects of concentration, pressure, and temperature changes on equilibrium, and the application of ICE tables. This summary is essential for A Level Chemistry students studying Edexcel Topic 11.
ChemistrySummary mind maps of each section in Unit 1 of Advanced Higher Chemistry.
ChemistryExplore Le Chatelier's Principle and its implications on chemical equilibrium in reversible reactions. This summary covers key concepts such as dynamic equilibrium, concentration shifts, and the behavior of systems in closed environments. Ideal for students seeking to understand how changes affect equilibrium states in chemistry.
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
Understanding where electrons live around an atom's nucleus isn't as simple as GCSE chemistry suggested. At A-level, you'll discover that electron shells are actually made up of different shaped regions called atomic orbitals, and there's a clever formula to work... Show more
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Remember from GCSE that electrons exist in electron shells around the nucleus? Well, scientists give each shell a number called the principal quantum number, written as "n". The first shell is n=1, the second is n=2, and so on.
Here's the brilliant bit: you can calculate the maximum number of electrons any shell can hold using the formula 2n². So shell 1 holds 2×1² = 2 electrons, shell 2 holds 2×2² = 8 electrons, shell 3 holds 18, and shell 4 holds 32 electrons.
But here's where it gets interesting - electrons aren't just floating around randomly in these shells. They occupy specific regions called atomic orbitals. Think of an atomic orbital as a 3D space around the nucleus where you're likely to find up to two electrons.
Key Point: Each orbital can hold a maximum of two electrons, but they must have opposite spins - one "up" and one "down".
The electrons behave like clouds of negative charge, and these clouds take on the actual shape of the orbital they're occupying. There are four main types of orbitals, each with its own letter: s, p, d, and f.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
S orbitals are the simplest - they're perfectly spherical, like a ball around the nucleus. Every single electron shell contains exactly one s orbital.
P orbitals look completely different - they're shaped like dumbbells or figure-8s. There are always three p orbitals in each shell, except for the first shell which doesn't have any p orbitals at all.
D orbitals are more complex, with five different d orbitals appearing in shell 3 and above. F orbitals are the most complicated, with seven different f orbitals that only show up in shell 4 and higher.
Remember: A subshell is just all the orbitals of the same type in one shell - like "2p" (all three p orbitals in shell 2) or "3d" (all five d orbitals in shell 3).
This explains why electron capacity jumps so dramatically as you move outward from the nucleus. Shell 1 only has an s orbital (2 electrons max), but shell 4 has s, p, d, and f orbitals, giving it space for 32 electrons total.
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.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore advanced concepts in chemical equilibrium, including equilibrium constants (Kc and Kp), the effects of concentration, pressure, and temperature changes on equilibrium, and the application of ICE tables. This summary is essential for A Level Chemistry students studying Edexcel Topic 11.
ChemistrySummary mind maps of each section in Unit 1 of Advanced Higher Chemistry.
ChemistryExplore Le Chatelier's Principle and its implications on chemical equilibrium in reversible reactions. This summary covers key concepts such as dynamic equilibrium, concentration shifts, and the behavior of systems in closed environments. Ideal for students seeking to understand how changes affect equilibrium states in chemistry.
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
Sociology