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Harper Jepps
04/12/2025
Chemistry
Topic 1 - atomic structure for GCSE chemistry
33
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4 Dec 2025
•
Atomic Structure - GCSE Chemistry Topic 1 Explained
H
Harper Jepps
@harperjepps
Evolution of Atomic Models & Element Groups
The atom's structure was discovered gradually through several brilliant scientists. John Dalton first proposed atoms as solid spheres, then J.J. Thompson suggested the "plum pudding model" with electrons embedded in a positive charge. Rutherford's gold foil experiment revealed that atoms contain mostly empty space with a charged nucleus.
Niels Bohr refined this with his nuclear model showing electrons orbiting in fixed shells, and James Chadwick later discovered neutrons. Meanwhile, Dmitri Mendeleev created the periodic table in 1869, arranging elements by atomic weight but leaving gaps for undiscovered elements—a strategy that later proved correct!
Transition metals have unique properties: they can form multiple ions, act as excellent catalysts (like nickel and iron in the Haber process), and typically display vibrant colours. Group 1 elements (alkali metals) increase in reactivity as you move down the group because the outer electron becomes easier to lose. They form 1+ ions, create ionic compounds with non-metals, and react vigorously with water.
Did you know? During Rutherford's famous gold foil experiment, he was so shocked when some alpha particles bounced back that he said it was "as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you!"
Halogens and Noble Gases
Group 7 elements (the halogens) all exist as pairs of atoms (diatomic molecules). Unlike most element groups, halogens become less reactive as you move down the group. This happens because it becomes harder for atoms to gain an electron when the outer shell is further from the nucleus.
Halogens form 1- ions (called halides) when bonding with metals. One fascinating reaction is the displacement reaction where a more reactive halogen will replace a less reactive one in a salt. For example, chlorine can displace bromine from sodium bromide solution.
Group 8 elements (the noble gases) are remarkably unreactive due to their full outer electron shells. These elements exist as single atoms (monatomic) rather than molecules and are all colourless at room temperature. As you travel down Group 8, the boiling points increase because larger atoms have stronger intermolecular forces.
Chemistry hack: Think of noble gases as the "loners" of the periodic table—they're so content with their full outer shells that they rarely interact with other elements!
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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
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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
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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
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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
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Best app on earth! no words because it’s too good
Thomas R
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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
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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
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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
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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
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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.
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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
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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
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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
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Atomic Structure - GCSE Chemistry Topic 1 Explained
H
Harper Jepps
@harperjepps
Welcome to the world of atomic structure! We'll explore how our understanding of the atom evolved through history and look at the key groups of elements that exist in the periodic table. Understanding these concepts will help you make sense... Show more
Evolution of Atomic Models & Element Groups
The atom's structure was discovered gradually through several brilliant scientists. John Dalton first proposed atoms as solid spheres, then J.J. Thompson suggested the "plum pudding model" with electrons embedded in a positive charge. Rutherford's gold foil experiment revealed that atoms contain mostly empty space with a charged nucleus.
Niels Bohr refined this with his nuclear model showing electrons orbiting in fixed shells, and James Chadwick later discovered neutrons. Meanwhile, Dmitri Mendeleev created the periodic table in 1869, arranging elements by atomic weight but leaving gaps for undiscovered elements—a strategy that later proved correct!
Transition metals have unique properties: they can form multiple ions, act as excellent catalysts (like nickel and iron in the Haber process), and typically display vibrant colours. Group 1 elements (alkali metals) increase in reactivity as you move down the group because the outer electron becomes easier to lose. They form 1+ ions, create ionic compounds with non-metals, and react vigorously with water.
Did you know? During Rutherford's famous gold foil experiment, he was so shocked when some alpha particles bounced back that he said it was "as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you!"
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Halogens and Noble Gases
Group 7 elements (the halogens) all exist as pairs of atoms (diatomic molecules). Unlike most element groups, halogens become less reactive as you move down the group. This happens because it becomes harder for atoms to gain an electron when the outer shell is further from the nucleus.
Halogens form 1- ions (called halides) when bonding with metals. One fascinating reaction is the displacement reaction where a more reactive halogen will replace a less reactive one in a salt. For example, chlorine can displace bromine from sodium bromide solution.
Group 8 elements (the noble gases) are remarkably unreactive due to their full outer electron shells. These elements exist as single atoms (monatomic) rather than molecules and are all colourless at room temperature. As you travel down Group 8, the boiling points increase because larger atoms have stronger intermolecular forces.
Chemistry hack: Think of noble gases as the "loners" of the periodic table—they're so content with their full outer shells that they rarely interact with other elements!
We thought you’d never ask...
What is the Knowunity AI companion?
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.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
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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