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Updated Mar 15, 2026
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Understanding Atomic Structure: Discoveries, Ions, and Isotopes
MikeG
@mikegilworth
1 / 4
Basic Atomic Structure
Every element is made up of just one type of atom - think of it like a pure ingredient in nature's recipe book. Carbon is only carbon atoms, oxygen is only oxygen atoms, and so on.
The basic atomic model shows atoms as having a tiny, dense centre called the nucleus (containing protons and neutrons) with electrons whizzing around the outside. It's a bit like a miniature solar system, but much more complex.
When writing chemical equations, you need to balance them so the same number of each type of atom appears on both sides. For example: 2Na + O₂ → 2Na₂O shows sodium reacting with oxygen to make sodium oxide.
Quick Tip: Remember that some elements like iodine (I₂) and chlorine (Cl₂) naturally exist as pairs of atoms joined together.
Separation Techniques
Scientists use different methods to separate mixtures depending on what they're trying to split up. Evaporation works by heating a liquid until it turns to gas, leaving any dissolved solids behind in the container.
Filtration is perfect when you want to separate a liquid from solid particles - the liquid passes through filter paper whilst the solid gets trapped. Chromatography cleverly separates different coloured dyes (like in ink) by letting them travel up special paper at different speeds.
Distillation is the go-to method for separating mixtures of liquids with different boiling points. The liquid with the lower boiling point evaporates first, gets cooled back into liquid form, and can be collected separately.
Real-world Connection: These techniques are used everywhere from making pure drinking water to creating perfumes and medicines.
Subatomic Particles and Atomic History
Inside every atom, you'll find three main particles with very different properties. Protons have a mass of 1 and a charge of +1, neutrons have a mass of 1 but no charge, whilst electrons are tiny with a charge of -1.
The mass number tells you the total protons plus neutrons, whilst the atomic number shows just the number of protons (which always equals the number of electrons in a neutral atom). These numbers help you identify any element.
Our understanding of atoms developed over centuries. Democritus first suggested everything was made of tiny, indivisible particles called "atomos". Much later, John Dalton pictured atoms as solid spheres, JJ Thomson discovered electrons and proposed the plum pudding model, Ernest Rutherford found the nucleus through his famous gold foil experiment, and James Chadwick discovered neutrons.
Memory Trick: The atomic number is like an element's ID number - it never changes and tells you exactly which element you're dealing with.
Ions, Isotopes and Atomic Models
Ions are atoms that have gained or lost electrons, giving them an electric charge. When an atom loses electrons, it becomes positively charged; when it gains electrons, it becomes negatively charged. For example, Mg²⁺ means a magnesium atom has lost 2 electrons.
Isotopes are atoms of the same element that have different numbers of neutrons. They behave chemically the same way but have slightly different masses - like identical twins with different weights.
The plum pudding model showed electrons scattered throughout a positive "pudding" of protons, but this was replaced by the nuclear model after Rutherford's experiments. The nuclear model correctly places protons and neutrons in a central nucleus with electrons in outer shells.
Key Point: Remember that protons and electrons are always equal in number for neutral atoms - it's only the neutrons that can vary in isotopes.
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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.
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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.
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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.
Rohan U
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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 Knowunity AI. 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 Knowunity AI. 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 Atomic Structure: Discoveries, Ions, and Isotopes
MikeG
@mikegilworth
Atoms are the tiny building blocks that make up everything around you - from your phone to the air you breathe. Understanding how these particles work and interact is essential for grasping chemistry concepts you'll use throughout your science studies.
Basic Atomic Structure
Every element is made up of just one type of atom - think of it like a pure ingredient in nature's recipe book. Carbon is only carbon atoms, oxygen is only oxygen atoms, and so on.
The basic atomic model shows atoms as having a tiny, dense centre called the nucleus (containing protons and neutrons) with electrons whizzing around the outside. It's a bit like a miniature solar system, but much more complex.
When writing chemical equations, you need to balance them so the same number of each type of atom appears on both sides. For example: 2Na + O₂ → 2Na₂O shows sodium reacting with oxygen to make sodium oxide.
Quick Tip: Remember that some elements like iodine (I₂) and chlorine (Cl₂) naturally exist as pairs of atoms joined together.
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Separation Techniques
Scientists use different methods to separate mixtures depending on what they're trying to split up. Evaporation works by heating a liquid until it turns to gas, leaving any dissolved solids behind in the container.
Filtration is perfect when you want to separate a liquid from solid particles - the liquid passes through filter paper whilst the solid gets trapped. Chromatography cleverly separates different coloured dyes (like in ink) by letting them travel up special paper at different speeds.
Distillation is the go-to method for separating mixtures of liquids with different boiling points. The liquid with the lower boiling point evaporates first, gets cooled back into liquid form, and can be collected separately.
Real-world Connection: These techniques are used everywhere from making pure drinking water to creating perfumes and medicines.
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Subatomic Particles and Atomic History
Inside every atom, you'll find three main particles with very different properties. Protons have a mass of 1 and a charge of +1, neutrons have a mass of 1 but no charge, whilst electrons are tiny with a charge of -1.
The mass number tells you the total protons plus neutrons, whilst the atomic number shows just the number of protons (which always equals the number of electrons in a neutral atom). These numbers help you identify any element.
Our understanding of atoms developed over centuries. Democritus first suggested everything was made of tiny, indivisible particles called "atomos". Much later, John Dalton pictured atoms as solid spheres, JJ Thomson discovered electrons and proposed the plum pudding model, Ernest Rutherford found the nucleus through his famous gold foil experiment, and James Chadwick discovered neutrons.
Memory Trick: The atomic number is like an element's ID number - it never changes and tells you exactly which element you're dealing with.
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Improve your grades
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Ions, Isotopes and Atomic Models
Ions are atoms that have gained or lost electrons, giving them an electric charge. When an atom loses electrons, it becomes positively charged; when it gains electrons, it becomes negatively charged. For example, Mg²⁺ means a magnesium atom has lost 2 electrons.
Isotopes are atoms of the same element that have different numbers of neutrons. They behave chemically the same way but have slightly different masses - like identical twins with different weights.
The plum pudding model showed electrons scattered throughout a positive "pudding" of protons, but this was replaced by the nuclear model after Rutherford's experiments. The nuclear model correctly places protons and neutrons in a central nucleus with electrons in outer shells.
Key Point: Remember that protons and electrons are always equal in number for neutral atoms - it's only the neutrons that can vary in isotopes.
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4.7/5
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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 Knowunity AI. 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 Knowunity AI. 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