Ever wondered what atoms actually look like? Scientists have been... Show more
English Literature
Biology
SociologySign 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
578
•
26 Dec 2025
•
Understanding the Evolution of Atomic Models
hiiii
@m_h112
The Evolution of Atomic Models
Back in ancient Greece, most people thought everything was made of just four elements: earth, air, fire, and water. But a philosopher called Democritus had a brilliant idea - he suggested that if you kept cutting something into smaller and smaller pieces, you'd eventually reach a point where it couldn't be cut anymore.
Dalton picked up this idea and proposed that atoms were like tiny, solid spheres - basically indestructible building blocks of matter. The word 'atom' actually comes from the Greek word 'atomos', meaning 'uncuttable'. This was a pretty good start, but scientists soon discovered there was much more to the story.
Thomson came along with his famous 'plum pudding' model. He'd discovered electrons and needed to explain how positive and negative charges worked together. His idea? Atoms were like a Christmas pudding - positive 'dough' with negative electrons dotted throughout like raisins.
Quick Tip: Remember these models by their nicknames - Dalton's 'solid sphere', Thomson's 'plum pudding', and you'll find the rest easier to follow!
Rutherford completely changed everything with his gold foil experiment. He fired tiny particles at an incredibly thin sheet of gold and watched what happened. Most particles went straight through (which was expected), but some bounced back completely - like throwing tennis balls at tissue paper and having them bounce off! This led to his nuclear model: a tiny, dense, positive nucleus surrounded by mostly empty space, with electrons somewhere on the outside.
Bohr refined Rutherford's model by suggesting electrons don't just float around randomly. Instead, they orbit the nucleus at specific energy levels - like planets orbiting the sun, but only at certain fixed distances. This explained why electrons have particular energy levels rather than just any old amount.
Finally, Chadwick solved a major puzzle. Scientists knew about protons (positive particles) in the nucleus, but the maths didn't add up - atoms were heavier than they should be. Chadwick proved the existence of neutrons - neutral particles that live in the nucleus alongside protons, making up the extra mass and keeping everything stable.
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.
Most popular content: Bohr Model
Most popular content in Chemistry
Most popular content
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
Understanding the Evolution of Atomic Models
hiiii
@m_h112
Ever wondered what atoms actually look like? Scientists have been trying to figure this out for thousands of years, and their ideas have changed dramatically as new evidence emerged. Let's explore how our understanding of atoms evolved from simple spheres... Show more
The Evolution of Atomic Models
Back in ancient Greece, most people thought everything was made of just four elements: earth, air, fire, and water. But a philosopher called Democritus had a brilliant idea - he suggested that if you kept cutting something into smaller and smaller pieces, you'd eventually reach a point where it couldn't be cut anymore.
Dalton picked up this idea and proposed that atoms were like tiny, solid spheres - basically indestructible building blocks of matter. The word 'atom' actually comes from the Greek word 'atomos', meaning 'uncuttable'. This was a pretty good start, but scientists soon discovered there was much more to the story.
Thomson came along with his famous 'plum pudding' model. He'd discovered electrons and needed to explain how positive and negative charges worked together. His idea? Atoms were like a Christmas pudding - positive 'dough' with negative electrons dotted throughout like raisins.
Quick Tip: Remember these models by their nicknames - Dalton's 'solid sphere', Thomson's 'plum pudding', and you'll find the rest easier to follow!
Rutherford completely changed everything with his gold foil experiment. He fired tiny particles at an incredibly thin sheet of gold and watched what happened. Most particles went straight through (which was expected), but some bounced back completely - like throwing tennis balls at tissue paper and having them bounce off! This led to his nuclear model: a tiny, dense, positive nucleus surrounded by mostly empty space, with electrons somewhere on the outside.
Bohr refined Rutherford's model by suggesting electrons don't just float around randomly. Instead, they orbit the nucleus at specific energy levels - like planets orbiting the sun, but only at certain fixed distances. This explained why electrons have particular energy levels rather than just any old amount.
Finally, Chadwick solved a major puzzle. Scientists knew about protons (positive particles) in the nucleus, but the maths didn't add up - atoms were heavier than they should be. Chadwick proved the existence of neutrons - neutral particles that live in the nucleus alongside protons, making up the extra mass and keeping everything stable.
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.
20
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Mock Exam
Quiz
Flashcards
Essay
Similar content
Evolution of Atomic Models
Explore the key developments in atomic theory from Dalton's solid spheres to the modern nuclear model. This summary covers major contributions by Thomson, Rutherford, Bohr, and Chadwick, detailing the structure of atoms and the discovery of protons and neutrons. Ideal for AQA GCSE Chemistry students preparing for paper 1.
Chemistry9
Chemistry: Bonding & Structure
Explore the key concepts of bonding and structure in chemistry, including ionic, covalent, and metallic bonding, as well as the properties of giant covalent structures and nanoparticles. This summary covers essential topics for GCSE students, focusing on particle theory, intermolecular forces, and the unique characteristics of various molecular structures. Ideal for active recall and exam preparation.
Chemistry9
States of Matter Overview
Explore the fundamental concepts of particles and the three states of matter: solids, liquids, and gases. This summary covers the arrangement and movement of particles, the kinetic molecular theory, and phase changes. Ideal for Year 7 students preparing for exams.
Chemistry7
Atomic Structure Overview
Explore the fundamental concepts of atomic structure, including atomic particles, subatomic particles, and the distinction between elements and compounds. This summary covers key theories from Dalton to Bohr, the discovery of protons, neutrons, and electrons, and methods for separating mixtures. Ideal for AQA Chemistry C1 revision.
Chemistry9
Atomic Model Evolution
Explore the evolution of atomic models from John Dalton's solid spheres to Rutherford's nuclear atom and Bohr's electron shells. This summary highlights key experiments and theories that shaped our understanding of atomic structure, making it essential for students studying chemistry and physics.
Chemistry9
Chemical Bonding Explained
Explore the fundamentals of chemical bonding, including ionic, covalent, and metallic structures. This summary covers the properties of solids, liquids, and gases, the formation of compounds, and the significance of giant covalent structures and nanoparticles. Ideal for AQA GCSE Chemistry Higher students seeking to understand the intricacies of molecular interactions and material properties.
Chemistry9
Most popular content: Bohr Model
Most popular content in Chemistry
Most popular content
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