Biology
Chemistry
AP Chemistry
English
AP English Literature
Chemistry
Dec 4, 2025
368
5 pages
Chelsea Tepsiri @chelseatep_
Ever wondered what everything around you is made of? It all comes down to atoms - the tiny... Show more
Think of atoms as the LEGO bricks of the universe - they're the smallest parts of elements that still keep their identity. Each element gets its own chemical symbol, like a name tag (think H for hydrogen, O for oxygen).
When two or more elements team up chemically, they form compounds. This isn't just mixing - it's like a chemical marriage that creates something completely new. You can only break up compounds using chemical reactions, not just by stirring or filtering.
Mixtures are totally different - imagine throwing different LEGO sets into one box. The pieces aren't stuck together, so you can separate them using simple methods like filtration or distillation. No chemical reactions needed!
Quick Tip If you can separate it physically (like picking out raisins from cereal), it's a mixture. If you need a chemical reaction, it's a compound!
Scientists once thought atoms were like tiny, solid snooker balls that couldn't be broken apart. Boy, were they wrong! The discovery of electrons led to the "plum-pudding model" - imagine a positively charged cake with negatively charged raisins (electrons) scattered throughout.
Everything changed with the alpha particle scattering experiment. Scientists fired particles at thin gold foil and watched where they went. Most went straight through, but some bounced back at weird angles - even straight back! This was like throwing tennis balls at tissue paper and having some bounce back at your face.
This experiment revealed that atoms have a tiny, dense nucleus at their centre where all the positive charge hangs out. Niels Bohr then figured out that electrons orbit this nucleus like planets around the sun.
Later discoveries by James Chadwick revealed neutrons - particles with no charge that live in the nucleus alongside protons.
Here's where atoms get their ID cards! The atomic number tells you how many protons an atom has - it's like an atom's fingerprint because every element has a unique number. The mass number is the total count of protons plus neutrons.
Isotopes are like siblings in the atomic world - same element (same number of protons) but different numbers of neutrons. They're basically the same person wearing different weight clothing!
Electronic structure shows how electrons arrange themselves in shells around the nucleus. For sodium (Na), it's 2,8,1 - meaning 2 electrons in the first shell, 8 in the second, and 1 lonely electron in the outer shell.
Memory Hack Think of electron shells like seats on a bus - the inner seats fill up first before anyone sits in the back!
Relative atomic mass is an average that accounts for all the different isotopes of an element and how common they are.
The periodic table arranges all elements by atomic number, and here's the genius bit - elements with similar properties line up in columns called groups. It's like organising your music playlist where all the rock songs are together!
Mendeleev was the mastermind behind this organisation, though he initially used atomic mass. He was so confident in his pattern that he left gaps for elements that hadn't been discovered yet - and he was right!
Metals hang out on the left side and love giving away electrons to form positive ions. Non-metals chill on the right and prefer grabbing electrons to form negative ions. This behaviour determines how elements react with each other.
Group 1 (alkali metals) are the drama queens of chemistry - they have one electron in their outer shell and react explosively with water. The bigger they get (going down the group), the more reactive they become!
Safety Note Never mess about with Group 1 metals in real life - they can literally explode when they touch water!
Group 0 (noble gases) are chemistry's loners - they have full outer shells (8 electrons, except helium with 2) and rarely react with anything. They're perfectly content on their own, which makes them super stable and unreactive.
Group 7 (halogens) are one electron short of happiness, so they're desperate to grab that missing electron. They'll react with metals to form ionic compounds or team up with non-metals to share electrons in covalent compounds.
As you travel down any group, patterns emerge. For halogens, molecular mass increases along with melting and boiling points - it's like they get heavier and need more energy to change state.
Pattern Spotter The periodic table is full of trends - once you spot one pattern, you can predict properties of elements you've never studied!
The beauty of the periodic table lies in its predictability - master the patterns, and you've cracked the code of chemistry!
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.
15
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the evolution of atomic models, including the Bohr model and the concept of atomic particles. This summary covers key concepts such as atomic structure, electronic configurations, isotopes, and the historical development of atomic theory. Ideal for students seeking a comprehensive understanding of atomic structure.
ChemistryDiscovery of atoms to 1937
ChemistryBasics of Atoms and theory including atom history.
ChemistryThis includes early chemical discoveries and atomic theory, electrons and other discoveries in the atomic physics.
ChemistryStudy note about the electron configuration
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
Chelsea Tepsiri
@chelseatep_
Ever wondered what everything around you is made of? It all comes down to atoms - the tiny building blocks that make up your phone, your lunch, even you! Understanding atomic structure and the periodic table is like having a... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think of atoms as the LEGO bricks of the universe - they're the smallest parts of elements that still keep their identity. Each element gets its own chemical symbol, like a name tag (think H for hydrogen, O for oxygen).
When two or more elements team up chemically, they form compounds. This isn't just mixing - it's like a chemical marriage that creates something completely new. You can only break up compounds using chemical reactions, not just by stirring or filtering.
Mixtures are totally different - imagine throwing different LEGO sets into one box. The pieces aren't stuck together, so you can separate them using simple methods like filtration or distillation. No chemical reactions needed!
Quick Tip: If you can separate it physically (like picking out raisins from cereal), it's a mixture. If you need a chemical reaction, it's a compound!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Scientists once thought atoms were like tiny, solid snooker balls that couldn't be broken apart. Boy, were they wrong! The discovery of electrons led to the "plum-pudding model" - imagine a positively charged cake with negatively charged raisins (electrons) scattered throughout.
Everything changed with the alpha particle scattering experiment. Scientists fired particles at thin gold foil and watched where they went. Most went straight through, but some bounced back at weird angles - even straight back! This was like throwing tennis balls at tissue paper and having some bounce back at your face.
This experiment revealed that atoms have a tiny, dense nucleus at their centre where all the positive charge hangs out. Niels Bohr then figured out that electrons orbit this nucleus like planets around the sun.
Later discoveries by James Chadwick revealed neutrons - particles with no charge that live in the nucleus alongside protons.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's where atoms get their ID cards! The atomic number tells you how many protons an atom has - it's like an atom's fingerprint because every element has a unique number. The mass number is the total count of protons plus neutrons.
Isotopes are like siblings in the atomic world - same element (same number of protons) but different numbers of neutrons. They're basically the same person wearing different weight clothing!
Electronic structure shows how electrons arrange themselves in shells around the nucleus. For sodium (Na), it's 2,8,1 - meaning 2 electrons in the first shell, 8 in the second, and 1 lonely electron in the outer shell.
Memory Hack: Think of electron shells like seats on a bus - the inner seats fill up first before anyone sits in the back!
Relative atomic mass is an average that accounts for all the different isotopes of an element and how common they are.
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 arranges all elements by atomic number, and here's the genius bit - elements with similar properties line up in columns called groups. It's like organising your music playlist where all the rock songs are together!
Mendeleev was the mastermind behind this organisation, though he initially used atomic mass. He was so confident in his pattern that he left gaps for elements that hadn't been discovered yet - and he was right!
Metals hang out on the left side and love giving away electrons to form positive ions. Non-metals chill on the right and prefer grabbing electrons to form negative ions. This behaviour determines how elements react with each other.
Group 1 (alkali metals) are the drama queens of chemistry - they have one electron in their outer shell and react explosively with water. The bigger they get (going down the group), the more reactive they become!
Safety Note: Never mess about with Group 1 metals in real life - they can literally explode when they touch water!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Group 0 (noble gases) are chemistry's loners - they have full outer shells (8 electrons, except helium with 2) and rarely react with anything. They're perfectly content on their own, which makes them super stable and unreactive.
Group 7 (halogens) are one electron short of happiness, so they're desperate to grab that missing electron. They'll react with metals to form ionic compounds or team up with non-metals to share electrons in covalent compounds.
As you travel down any group, patterns emerge. For halogens, molecular mass increases along with melting and boiling points - it's like they get heavier and need more energy to change state.
Pattern Spotter: The periodic table is full of trends - once you spot one pattern, you can predict properties of elements you've never studied!
The beauty of the periodic table lies in its predictability - master the patterns, and you've cracked the code of chemistry!
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.
15
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the evolution of atomic models, including the Bohr model and the concept of atomic particles. This summary covers key concepts such as atomic structure, electronic configurations, isotopes, and the historical development of atomic theory. Ideal for students seeking a comprehensive understanding of atomic structure.
ChemistryDiscovery of atoms to 1937
ChemistryBasics of Atoms and theory including atom history.
ChemistryThis includes early chemical discoveries and atomic theory, electrons and other discoveries in the atomic physics.
ChemistryStudy note about the electron configuration
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
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