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Olamide
02/12/2025
Chemistry
Chemistry topic 1: Atomic structure
168
•
2 Dec 2025
•
Understanding Atomic Structure: Basics of Chemistry
Olamide
@olamide_26
1 / 3
Atomic Structure Basics
Atoms are the smallest possible pieces of an element, with a radius of just 0.1nm. Think of them as incredibly tiny LEGO blocks that make up everything in the universe. Each atom has a nucleus at its centre containing protons (positive charge) and neutrons (no charge), with electrons (negative charge) whizzing around in shells.
Understanding the difference between elements, compounds, and mixtures is crucial for your exams. An element contains atoms with the same atomic number, whilst a compound has different atoms bonded together. Isotopes are atoms with the same protons but different neutrons - like different versions of the same element.
The periodic table makes finding particle numbers dead easy. The smaller number gives you protons and electrons, whilst neutrons equal the big number minus the small number. Scientists like Dalton, Thomson, and Rutherford gradually discovered these particles, evolving our understanding from solid spheres to the complex atomic model we use today.
Quick Tip: Remember that atoms are electrically neutral because they have equal numbers of protons and electrons!
The Periodic Table and Element Properties
Dmitri Mendeleev created the periodic table by arranging elements by atomic mass and chemical properties. His genius move? Leaving gaps for undiscovered elements, which later proved spot-on when new elements were found that perfectly filled those spaces.
The periodic table's layout is brilliantly logical. Groups (vertical columns) tell you the number of outer electrons, whilst periods (horizontal rows) show the number of electron shells. Group 1 elements have 1 outer electron, Group 7 have 7, and so on.
Metals and non-metals have opposite properties that are easy to remember. Metals are dense, strong, malleable, and conduct heat and electricity well. Non-metals are light, weak, brittle, and act as insulators (except graphite). This knowledge is goldmine material for exam questions.
Electron arrangement follows simple rules: fill shells from inside out, with the first shell holding 2 electrons and the second and third holding 8 each. Master this pattern and you'll ace electron configuration questions.
Exam Focus: Group numbers directly tell you outer electrons AND the charge ions will form - incredibly useful for predictions!
Group Properties and Separation Techniques
Group 1 (alkali metals) and Group 7 (halogens) show clear trends that examiners love testing. As you go down Group 1, reactivity increases whilst melting point decreases. Group 7 does the opposite - reactivity decreases down the group whilst melting point increases. Group 0 (noble gases) are completely inert and don't react at all.
Transition metals (Triple Science only) are the workhorses of the periodic table. They're denser, harder, and stronger than Group 1 metals, with higher melting points but lower reactivity. They form coloured compounds and make excellent catalysts.
Separation techniques are practical skills you'll definitely use in practicals. Chromatography separates dyes, filtration removes insoluble solids, whilst evaporation and crystallisation both recover salts from solutions. Simple distillation separates liquids from solutions, and fractional distillation separates liquid mixtures with different boiling points.
These techniques aren't just for exams - they're used everywhere from water treatment to making perfumes. Understanding when to use each method shows you're thinking like a real chemist.
Practical Tip: Remember that crystallisation gives you better quality crystals than evaporation because the gentler heating prevents decomposition!
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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
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 Atomic Structure: Basics of Chemistry
Olamide
@olamide_26
Ever wondered what makes up everything around you? From your phone to the air you breathe, it all comes down to atoms - the tiny building blocks of matter that are so small you'd need 10 billion of them lined... Show more
Atomic Structure Basics
Atoms are the smallest possible pieces of an element, with a radius of just 0.1nm. Think of them as incredibly tiny LEGO blocks that make up everything in the universe. Each atom has a nucleus at its centre containing protons (positive charge) and neutrons (no charge), with electrons (negative charge) whizzing around in shells.
Understanding the difference between elements, compounds, and mixtures is crucial for your exams. An element contains atoms with the same atomic number, whilst a compound has different atoms bonded together. Isotopes are atoms with the same protons but different neutrons - like different versions of the same element.
The periodic table makes finding particle numbers dead easy. The smaller number gives you protons and electrons, whilst neutrons equal the big number minus the small number. Scientists like Dalton, Thomson, and Rutherford gradually discovered these particles, evolving our understanding from solid spheres to the complex atomic model we use today.
Quick Tip: Remember that atoms are electrically neutral because they have equal numbers of protons and electrons!
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The Periodic Table and Element Properties
Dmitri Mendeleev created the periodic table by arranging elements by atomic mass and chemical properties. His genius move? Leaving gaps for undiscovered elements, which later proved spot-on when new elements were found that perfectly filled those spaces.
The periodic table's layout is brilliantly logical. Groups (vertical columns) tell you the number of outer electrons, whilst periods (horizontal rows) show the number of electron shells. Group 1 elements have 1 outer electron, Group 7 have 7, and so on.
Metals and non-metals have opposite properties that are easy to remember. Metals are dense, strong, malleable, and conduct heat and electricity well. Non-metals are light, weak, brittle, and act as insulators (except graphite). This knowledge is goldmine material for exam questions.
Electron arrangement follows simple rules: fill shells from inside out, with the first shell holding 2 electrons and the second and third holding 8 each. Master this pattern and you'll ace electron configuration questions.
Exam Focus: Group numbers directly tell you outer electrons AND the charge ions will form - incredibly useful for predictions!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Group Properties and Separation Techniques
Group 1 (alkali metals) and Group 7 (halogens) show clear trends that examiners love testing. As you go down Group 1, reactivity increases whilst melting point decreases. Group 7 does the opposite - reactivity decreases down the group whilst melting point increases. Group 0 (noble gases) are completely inert and don't react at all.
Transition metals (Triple Science only) are the workhorses of the periodic table. They're denser, harder, and stronger than Group 1 metals, with higher melting points but lower reactivity. They form coloured compounds and make excellent catalysts.
Separation techniques are practical skills you'll definitely use in practicals. Chromatography separates dyes, filtration removes insoluble solids, whilst evaporation and crystallisation both recover salts from solutions. Simple distillation separates liquids from solutions, and fractional distillation separates liquid mixtures with different boiling points.
These techniques aren't just for exams - they're used everywhere from water treatment to making perfumes. Understanding when to use each method shows you're thinking like a real chemist.
Practical Tip: Remember that crystallisation gives you better quality crystals than evaporation because the gentler heating prevents decomposition!
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?
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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Most popular content: Periodic Table
Most popular content in Chemistry
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Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
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