Biology
Chemistry
AP Chemistry
English
AP English Literature
Chemistry
Nov 22, 2025
160
4 pages
Tiya @tiya_2006
Atoms are the basic building blocks of everything around you! These tiny particles come together to form all... Show more
Scientists have been trying to figure out atoms for centuries! It all started with Democritus in 450 BC, who first suggested that matter consists of tiny, indivisible particles. John Dalton brought this idea into modern chemistry in 1803, proposing that atoms are the building blocks of all matter.
The model of the atom evolved dramatically over time. J.J. Thomson discovered electrons in 1895 and created the "Plum Pudding Model," while Rutherford revealed in 1910 that atoms consist mostly of empty space with a concentrated positive nucleus. Bohr improved this in 1922 by showing that electrons travel in specific orbits.
The most recent developments came from Schrödinger, who introduced the Electron Cloud Model in 1926, suggesting electrons exist in probability clouds rather than fixed paths. Chadwick completed our basic understanding in 1932 by discovering neutrons in the nucleus.
Fun Fact Our understanding of atoms has changed dramatically over 2,500 years - from simple indivisible particles to complex structures with nuclei, electron clouds, and different energy levels!
The valence electrons in the outermost shell are super important! They determine whether an atom becomes an anion or cation and control how atoms bond to form different chemicals. According to the Octet Rule, atoms "want" to have a complete outer shell of 8 electrons and will gain, lose, or share electrons to achieve this.
The periodic table organizes elements based on their properties. Elements are arranged in vertical groups (columns) and horizontal rows. As you move from left to right across the table, elements generally become more stable (except for hydrogen). Group 1 elements (Alkali metals) and Group 7 elements (Halogens) are extremely unstable, while Group 8 elements (Noble Gases) are stable.
You can draw a Lewis Dot Diagram to show an element's valence electrons simply by placing dots around the element's symbol. This helps visualize how atoms might interact with each other to reach a stable electron configuration.
Test Prep Alert Know how to quickly determine an element's valence electrons by looking at its group number in the periodic table. This is essential for predicting chemical behavior!
The periodic table is organized with amazing logic! Groups (vertical columns) contain elements with similar chemical properties because they have the same number of valence electrons. Rows show trends in stability from left to right.
Elements are categorized into families based on their properties. Alkali metals (Group 1) and Halogens (Group 7) are extremely unstable, while Noble Gases (Group 8) are stable with full outer shells. Other important groups include Alkaline Earth metals (Group 2), Carbon group (Group 4), and Oxygen group (Group 6).
Remember these key equations Atomic number equals the number of protons; Atomic mass is protons plus neutrons; and the number of electrons equals the number of protons in a neutral atom. As you move down the periodic table, elements have more electron orbitals, making them generally larger.
Make Connections Notice how the position of an element in the periodic table tells you almost everything about how it behaves chemically. The table isn't just organized - it's predictive!
The Bohr Model gives us a simple way to visualize atoms. At the center is the nucleus containing protons (positive charge) and neutrons (neutral). Around the nucleus, electrons (negative charge) orbit in specific paths called electron orbits or shells.
This model, though simplified, helps us understand why elements react the way they do. The electrons in the outermost orbit (valence electrons) determine chemical behavior. Elements with similar valence electron arrangements behave similarly, which explains the periodic table's organization.
Each element has a unique "identity card" based on its atomic structure. The atomic number tells you how many protons it has, the electron configuration shows how its electrons are arranged, and isotopes represent variations in neutron numbers. Together, these features determine everything from an element's physical properties to its chemical reactivity.
Perspective Shift While we draw atoms as little solar systems with electrons orbiting like planets, remember that the actual size of an atom is mind-boggling small - if an atom were the size of a football stadium, its nucleus would be smaller than a pea in the center!
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
2
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Discovery of atoms to 1937
ChemistryExplore the fundamentals of atomic structure and the periodic table in this comprehensive summary. Understand key concepts such as atomic number, mass number, subatomic particles, and the classification of elements into groups. This resource covers the development of atomic models, the properties of noble gases, halogens, and alkali metals, as well as periodic trends in reactivity and physical properties. Ideal for students studying chemistry.
Chemistryimportant scientists and experiments that contributed to the current atomic model
ChemistryStudy note about the electron configuration
ChemistryLearning electron configuration, the model of an atom, sub level, orbital, Augsburg principle, etc.
ChemistryRadioactive chemicals, Decay, Nuclear Fission&Fusion
ChemistryApp 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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Tiya
@tiya_2006
Atoms are the basic building blocks of everything around you! These tiny particles come together to form all matter in the universe. Understanding atoms helps you make sense of chemistry, physics, and how the world works at its smallest level.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Scientists have been trying to figure out atoms for centuries! It all started with Democritus in 450 BC, who first suggested that matter consists of tiny, indivisible particles. John Dalton brought this idea into modern chemistry in 1803, proposing that atoms are the building blocks of all matter.
The model of the atom evolved dramatically over time. J.J. Thomson discovered electrons in 1895 and created the "Plum Pudding Model," while Rutherford revealed in 1910 that atoms consist mostly of empty space with a concentrated positive nucleus. Bohr improved this in 1922 by showing that electrons travel in specific orbits.
The most recent developments came from Schrödinger, who introduced the Electron Cloud Model in 1926, suggesting electrons exist in probability clouds rather than fixed paths. Chadwick completed our basic understanding in 1932 by discovering neutrons in the nucleus.
Fun Fact: Our understanding of atoms has changed dramatically over 2,500 years - from simple indivisible particles to complex structures with nuclei, electron clouds, and different energy levels!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The valence electrons in the outermost shell are super important! They determine whether an atom becomes an anion or cation and control how atoms bond to form different chemicals. According to the Octet Rule, atoms "want" to have a complete outer shell of 8 electrons and will gain, lose, or share electrons to achieve this.
The periodic table organizes elements based on their properties. Elements are arranged in vertical groups (columns) and horizontal rows. As you move from left to right across the table, elements generally become more stable (except for hydrogen). Group 1 elements (Alkali metals) and Group 7 elements (Halogens) are extremely unstable, while Group 8 elements (Noble Gases) are stable.
You can draw a Lewis Dot Diagram to show an element's valence electrons simply by placing dots around the element's symbol. This helps visualize how atoms might interact with each other to reach a stable electron configuration.
Test Prep Alert: Know how to quickly determine an element's valence electrons by looking at its group number in the periodic table. This is essential for predicting chemical behavior!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The periodic table is organized with amazing logic! Groups (vertical columns) contain elements with similar chemical properties because they have the same number of valence electrons. Rows show trends in stability from left to right.
Elements are categorized into families based on their properties. Alkali metals (Group 1) and Halogens (Group 7) are extremely unstable, while Noble Gases (Group 8) are stable with full outer shells. Other important groups include Alkaline Earth metals (Group 2), Carbon group (Group 4), and Oxygen group (Group 6).
Remember these key equations: Atomic number equals the number of protons; Atomic mass is protons plus neutrons; and the number of electrons equals the number of protons in a neutral atom. As you move down the periodic table, elements have more electron orbitals, making them generally larger.
Make Connections: Notice how the position of an element in the periodic table tells you almost everything about how it behaves chemically. The table isn't just organized - it's predictive!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Bohr Model gives us a simple way to visualize atoms. At the center is the nucleus containing protons (positive charge) and neutrons (neutral). Around the nucleus, electrons (negative charge) orbit in specific paths called electron orbits or shells.
This model, though simplified, helps us understand why elements react the way they do. The electrons in the outermost orbit (valence electrons) determine chemical behavior. Elements with similar valence electron arrangements behave similarly, which explains the periodic table's organization.
Each element has a unique "identity card" based on its atomic structure. The atomic number tells you how many protons it has, the electron configuration shows how its electrons are arranged, and isotopes represent variations in neutron numbers. Together, these features determine everything from an element's physical properties to its chemical reactivity.
Perspective Shift: While we draw atoms as little solar systems with electrons orbiting like planets, remember that the actual size of an atom is mind-boggling small - if an atom were the size of a football stadium, its nucleus would be smaller than a pea in the center!
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
2
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Discovery of atoms to 1937
ChemistryExplore the fundamentals of atomic structure and the periodic table in this comprehensive summary. Understand key concepts such as atomic number, mass number, subatomic particles, and the classification of elements into groups. This resource covers the development of atomic models, the properties of noble gases, halogens, and alkali metals, as well as periodic trends in reactivity and physical properties. Ideal for students studying chemistry.
Chemistryimportant scientists and experiments that contributed to the current atomic model
ChemistryStudy note about the electron configuration
ChemistryLearning electron configuration, the model of an atom, sub level, orbital, Augsburg principle, etc.
ChemistryRadioactive chemicals, Decay, Nuclear Fission&Fusion
ChemistryApp 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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
