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
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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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2
0
AK Squad
03/12/2025
Physics
Atomic Structure
75
•
3 Dec 2025
•
AK Squad
@aksquad_hoka
Understanding atomic structure and nuclear radiation is crucial for GCSE... Show more
Your mobile phone contains billions of atoms, each incredibly tiny at just 1 × 10⁻¹⁰ metres across. Think of an atom like a football stadium where the nucleus is a marble at the centre - that's how much empty space there is!
Every atom has a nucleus (containing protons and neutrons) surrounded by electrons whizzing around at different energy levels. The number of protons equals the number of electrons, keeping the atom electrically neutral. Isotopes are atoms of the same element with different numbers of neutrons - like different versions of the same thing.
Scientists didn't always know this structure. They started with the idea that atoms were solid spheres, then discovered the plum pudding model (electrons stuck in positive "pudding"). The famous alpha scattering experiment proved atoms have a dense nucleus, leading to our modern understanding.
Key insight: Most of an atom's mass is crammed into the tiny nucleus - imagine all of a football stadium's weight squeezed into a marble at the centre!
Some atomic nuclei are like wobbly chairs - they're unstable and need to release energy to become stable through radioactive decay. This happens randomly, like popcorn popping - you can't predict exactly when each kernel will pop.
There are three main types of nuclear radiation. Alpha particles are chunky but easily stopped by paper. Beta particles are fast electrons that can penetrate further but are stopped by aluminium. Gamma rays are electromagnetic radiation that can penetrate deeply and need thick lead or concrete to stop them.
Half-life is the time it takes for half of a radioactive sample to decay. If you start with 1000 radioactive nuclei and the half-life is 5 years, you'll have 500 left after 5 years, 250 after 10 years, and so on.
Background radiation is everywhere around us - from rocks, cosmic rays, and even man-made sources like nuclear weapons testing. Contamination means radioactive material gets on you, whilst irradiation means radiation passes through you without making you radioactive.
Remember: Radiation dose is measured in Sieverts (Sv) - this tells you how much biological damage the radiation might cause.
Doctors use gamma rays as medical tracers to see inside your body and in radiotherapy to destroy cancer cells. It's like having a tiny lighthouse inside you that doctors can track, or a precise weapon targeting only the bad cells.
Nuclear fission is when large, unstable nuclei (like uranium) split apart after absorbing a neutron. This creates two smaller nuclei, releases 2-3 new neutrons, plus loads of energy. If those neutrons hit other nuclei, you get a chain reaction.
In nuclear power stations, control rods are lowered or raised to absorb neutrons and control the reaction rate - like having brakes on a car. The energy released heats water into steam, which spins turbines to generate electricity. Without control rods, you'd get an uncontrolled explosion like in nuclear weapons.
The benefits of medical radiation often outweigh the risks. Yes, radiation can cause future health problems, but if it can cure your cancer today, most people choose treatment. It's about weighing up immediate life-saving benefits against small future risks.
Think about it: Nuclear fission in power stations is just a very carefully controlled version of what happens in nuclear weapons - the difference is all about control.
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
AK Squad
@aksquad_hoka
Understanding atomic structure and nuclear radiation is crucial for GCSE physics and chemistry. This topic covers everything from the tiny particles that make up atoms to how nuclear power works, plus the medical uses of radiation that could save lives.
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Your mobile phone contains billions of atoms, each incredibly tiny at just 1 × 10⁻¹⁰ metres across. Think of an atom like a football stadium where the nucleus is a marble at the centre - that's how much empty space there is!
Every atom has a nucleus (containing protons and neutrons) surrounded by electrons whizzing around at different energy levels. The number of protons equals the number of electrons, keeping the atom electrically neutral. Isotopes are atoms of the same element with different numbers of neutrons - like different versions of the same thing.
Scientists didn't always know this structure. They started with the idea that atoms were solid spheres, then discovered the plum pudding model (electrons stuck in positive "pudding"). The famous alpha scattering experiment proved atoms have a dense nucleus, leading to our modern understanding.
Key insight: Most of an atom's mass is crammed into the tiny nucleus - imagine all of a football stadium's weight squeezed into a marble at the centre!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Some atomic nuclei are like wobbly chairs - they're unstable and need to release energy to become stable through radioactive decay. This happens randomly, like popcorn popping - you can't predict exactly when each kernel will pop.
There are three main types of nuclear radiation. Alpha particles are chunky but easily stopped by paper. Beta particles are fast electrons that can penetrate further but are stopped by aluminium. Gamma rays are electromagnetic radiation that can penetrate deeply and need thick lead or concrete to stop them.
Half-life is the time it takes for half of a radioactive sample to decay. If you start with 1000 radioactive nuclei and the half-life is 5 years, you'll have 500 left after 5 years, 250 after 10 years, and so on.
Background radiation is everywhere around us - from rocks, cosmic rays, and even man-made sources like nuclear weapons testing. Contamination means radioactive material gets on you, whilst irradiation means radiation passes through you without making you radioactive.
Remember: Radiation dose is measured in Sieverts (Sv) - this tells you how much biological damage the radiation might cause.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Doctors use gamma rays as medical tracers to see inside your body and in radiotherapy to destroy cancer cells. It's like having a tiny lighthouse inside you that doctors can track, or a precise weapon targeting only the bad cells.
Nuclear fission is when large, unstable nuclei (like uranium) split apart after absorbing a neutron. This creates two smaller nuclei, releases 2-3 new neutrons, plus loads of energy. If those neutrons hit other nuclei, you get a chain reaction.
In nuclear power stations, control rods are lowered or raised to absorb neutrons and control the reaction rate - like having brakes on a car. The energy released heats water into steam, which spins turbines to generate electricity. Without control rods, you'd get an uncontrolled explosion like in nuclear weapons.
The benefits of medical radiation often outweigh the risks. Yes, radiation can cause future health problems, but if it can cure your cancer today, most people choose treatment. It's about weighing up immediate life-saving benefits against small future risks.
Think about it: Nuclear fission in power stations is just a very carefully controlled version of what happens in nuclear weapons - the difference is all about control.
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 fundamentals of radioactivity, including alpha, beta, and gamma decay, half-life calculations, and the properties of isotopes. This summary covers key concepts such as nuclear radiation, energy levels, and the differences between contamination and irradiation. Ideal for students preparing for exams in combined science.
PhysicsExplore the different types of radiation, including Alpha, Beta, and Gamma rays. This summary covers their properties, penetration abilities, ionizing capabilities, and practical applications in fields like sterilization and cancer treatment. Ideal for AQA Combined Science students.
PhysicsExplore the evolution of atomic theory, from early concepts by Democritus to modern atomic models. Understand key principles such as atomic structure, periodic table development, and the role of isotopes. This summary covers essential topics including energy forms, oxidation states, and the contributions of notable scientists like Dalton, Thompson, and Bohr. Ideal for students studying chemistry and physics.
PhysicsExplore the fundamentals of atomic structure and nuclear radiation in this comprehensive study resource. Covering key concepts such as isotopes, radioactive decay, nuclear fission, and the historical development of atomic models, this summary is designed for GCSE Physics students preparing for AQA Higher Triple exams. Enhance your understanding of protons, neutrons, and the properties of alpha, beta, and gamma radiation.
PhysicsExplore the fundamentals of atomic structure, including key concepts such as nuclear fission, fusion, radioactive decay, and the properties of subatomic particles. This comprehensive resource includes past exam questions and mark schemes to help you identify and strengthen your understanding of atomic theory and its applications in physics.
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PhysicsQuotes 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