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
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
Show all topics
Chemistry
7 Dec 2025
48
3 pages
yan yanni @yanyanni_diyn
Nuclear radiation might sound scary, but understanding how atoms break down is actually quite straightforward once you grasp... Show more
Ever wondered what makes some atoms unstable whilst others stay perfectly fine for millions of years? It all comes down to the nucleus - that tiny centre of an atom that's 10,000 times smaller than the atom itself.
Your body contains loads of stable atoms like carbon-12, but also some unstable ones like carbon-14. When atoms are unstable, they undergo radioactive decay - basically falling apart to become more stable. The tricky bit is that this process is completely random, so you can't predict exactly when any individual atom will decay.
There are four main types of decay you need to know alpha, beta, gamma, and neutron decay. Each one changes the atom in different ways by releasing different particles.
Alpha decay happens when an unstable nucleus spits out an alpha particle (which is actually just a helium nucleus containing 2 protons and 2 neutrons). When this happens, the original atom loses 4 from its mass number and 2 from its atomic number. For example, uranium-238 becomes thorium-234 plus an alpha particle.
Quick Tip In nuclear equations, the numbers must always balance on both sides - mass numbers on top, atomic numbers on bottom!
Beta decay is pretty clever - it happens when a neutron inside the nucleus transforms into a proton, shooting out a fast-moving electron called a beta particle. Unlike alpha decay, the mass number stays exactly the same, but the atomic number increases by 1 because there's now an extra proton.
Think of carbon-14 turning into nitrogen-14 - same mass, but one more proton makes it a completely different element. This is why beta decay is so important in things like carbon dating!
Gamma decay is quite different because it doesn't involve particles at all. Instead, the nucleus releases gamma rays - extremely high-energy electromagnetic waves . This happens when a nucleus is in an "excited state" and needs to release energy to become more stable.
The brilliant thing about gamma rays is that they don't change the atom's mass or atomic number at all - they just release excess energy. Medical isotopes like iodine-131 often undergo beta decay followed by gamma emission, which is why they're useful for treating thyroid conditions.
Remember Beta particles are electrons with a -1 charge, whilst gamma rays have no mass or charge whatsoever!
Here's where radiation gets really practical - different types can be stopped by completely different materials. Alpha particles are actually quite wimpy and can be stopped by a simple sheet of paper, whilst beta particles need aluminium to block them properly. Gamma rays, however, are proper tough and need thick lead to stop them.
This makes sense when you think about their range in air too. Alpha particles fizzle out after just 5cm, beta particles can travel anywhere from 10cm to several metres, but gamma rays can travel extremely long distances through air.
Scientists detect radiation using a Geiger-Müller tube (GM tube) connected to a ratemeter that counts radiation in "counts per second". The clever bit is that GM tubes always detect some background radiation - there's always a small amount of natural radiation around us.
When you place a radioactive source near the detector, the count rate shoots up dramatically. This is how researchers can measure different types of radiation and work out which materials best protect us from each type.
Fun Fact The background radiation you're exposed to right now is completely normal and mostly comes from cosmic rays and natural radioactive elements in rocks!
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
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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
yan yanni
@yanyanni_diyn
Nuclear radiation might sound scary, but understanding how atoms break down is actually quite straightforward once you grasp the basics. When certain atoms become unstable, they release energy and particles in predictable ways, creating three main types of radiation that... Show more
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered what makes some atoms unstable whilst others stay perfectly fine for millions of years? It all comes down to the nucleus - that tiny centre of an atom that's 10,000 times smaller than the atom itself.
Your body contains loads of stable atoms like carbon-12, but also some unstable ones like carbon-14. When atoms are unstable, they undergo radioactive decay - basically falling apart to become more stable. The tricky bit is that this process is completely random, so you can't predict exactly when any individual atom will decay.
There are four main types of decay you need to know: alpha, beta, gamma, and neutron decay. Each one changes the atom in different ways by releasing different particles.
Alpha decay happens when an unstable nucleus spits out an alpha particle (which is actually just a helium nucleus containing 2 protons and 2 neutrons). When this happens, the original atom loses 4 from its mass number and 2 from its atomic number. For example, uranium-238 becomes thorium-234 plus an alpha particle.
Quick Tip: In nuclear equations, the numbers must always balance on both sides - mass numbers on top, atomic numbers on bottom!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Beta decay is pretty clever - it happens when a neutron inside the nucleus transforms into a proton, shooting out a fast-moving electron called a beta particle. Unlike alpha decay, the mass number stays exactly the same, but the atomic number increases by 1 because there's now an extra proton.
Think of carbon-14 turning into nitrogen-14 - same mass, but one more proton makes it a completely different element. This is why beta decay is so important in things like carbon dating!
Gamma decay is quite different because it doesn't involve particles at all. Instead, the nucleus releases gamma rays - extremely high-energy electromagnetic waves . This happens when a nucleus is in an "excited state" and needs to release energy to become more stable.
The brilliant thing about gamma rays is that they don't change the atom's mass or atomic number at all - they just release excess energy. Medical isotopes like iodine-131 often undergo beta decay followed by gamma emission, which is why they're useful for treating thyroid conditions.
Remember: Beta particles are electrons with a -1 charge, whilst gamma rays have no mass or charge whatsoever!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's where radiation gets really practical - different types can be stopped by completely different materials. Alpha particles are actually quite wimpy and can be stopped by a simple sheet of paper, whilst beta particles need aluminium to block them properly. Gamma rays, however, are proper tough and need thick lead to stop them.
This makes sense when you think about their range in air too. Alpha particles fizzle out after just 5cm, beta particles can travel anywhere from 10cm to several metres, but gamma rays can travel extremely long distances through air.
Scientists detect radiation using a Geiger-Müller tube (GM tube) connected to a ratemeter that counts radiation in "counts per second". The clever bit is that GM tubes always detect some background radiation - there's always a small amount of natural radiation around us.
When you place a radioactive source near the detector, the count rate shoots up dramatically. This is how researchers can measure different types of radiation and work out which materials best protect us from each type.
Fun Fact: The background radiation you're exposed to right now is completely normal and mostly comes from cosmic rays and natural radioactive elements in rocks!
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.
1
Smart Tools NEW
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