Subjects
Biology
Chemistry
AP Chemistry
English
AP English Literature
Chemistry
Dec 9, 2025
111
4 pages
Yujun Ge @yujunge_jflh
Atoms and elements are the building blocks of everything around you. Understanding atomic structure helps explain how elements... Show more
Atoms are the smallest units of matter that cannot be broken down by chemical means. Think of atoms as the tiny "LEGO pieces" that build everything you can touch, see, or smell!
Every atom has three main parts working together. At the center is the nucleus, which contains protons (positively charged particles) and neutrons (particles with no charge). Electrons (negatively charged particles) orbit around the nucleus in specific arrangements called energy levels.
The atomic number of an element equals the number of protons in its nucleus. This number determines what element it is! The atomic mass is calculated by adding the protons and neutrons together. In a neutral atom, the number of electrons always equals the number of protons.
Quick Tip Remember that protons and neutrons live together in the nucleus, while electrons move around outside. The number of protons (atomic number) tells you which element you're looking at!
Electrons aren't just randomly floating around atoms—they organize themselves in specific energy levels (sometimes called shells). Each level has a maximum capacity the first level holds 2 electrons, the second and third can each hold 8, and the fourth can hold up to 18 electrons.
Elements are pure substances made of only one kind of atom. The number of electrons in a neutral atom always equals its number of protons. This balance keeps the atom electrically neutral (no charge).
When atoms gain or lose electrons, they become ions—particles with an electrical charge. If an atom loses electrons, it becomes a cation with a positive charge . If an atom gains electrons, it becomes an anion with a negative charge. Ions are written with a + or - superscript, like Ca²⁺.
Remember This You never change the number of protons when forming ions—only electrons move! Losing electrons makes an atom positive, while gaining electrons makes it negative.
Isotopes are variants of the same element with different numbers of neutrons. Think of them as siblings from the same family—same number of protons but different weights because of varying neutron counts. When isotopes are unstable, they're radioactive and undergo decay to reach a more stable form.
The periodic table isn't just a random arrangement of elements—it's organized by increasing atomic number (number of protons). Elements in the same column (group) have the same number of valence electrons, which gives them similar chemical properties. The rows (periods) correspond to the number of electron shells an atom has.
The periodic table is divided into different "blocks" based on which type of orbital is being filled with electrons. This organization helps chemists predict how elements will behave in reactions.
Chemistry Hack The group number on the periodic table often tells you how many valence electrons an element has—which helps predict how it will bond with other elements!
Valence electrons—the electrons in the outermost energy level—are the key players in forming chemical bonds. Scientists use Lewis dot diagrams to visually represent these valence electrons around element symbols.
There are three major types of bonds that atoms form. Covalent bonds occur when two nonmetal atoms share electron pairs (always an even number like 2, 4, or 6). A simple example is hydrogen gas (H₂), where two hydrogen atoms share their electrons.
Ionic bonds form through electron transfer rather than sharing. When a metal atom gives electrons to a nonmetal atom, the resulting oppositely charged ions attract each other. Sodium chloride (NaCl) is a classic example—sodium gives an electron to chlorine.
Hydrogen bonds are special attractions that form when hydrogen (with a partial positive charge) is attracted to another atom with a negative charge. These bonds might be weaker than the others, but they're crucial for many biological processes!
Bonding Insight Think of covalent bonds as "sharing" and ionic bonds as "giving and taking." The type of elements involved (metals vs. nonmetals) usually determines which type of bond will form.
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.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Lewis dot structures how to with examples
ChemistryThese notes help inform you on the basics of Chemistry and get you used to the terms used in this subject.
ChemistryAtomic Radius & Ionization Energy
ChemistryExplore the properties, reactivity trends, and bonding characteristics of Group 7 elements (halogens). This summary covers the increasing atomic size, the nature of covalent and ionic bonds, and displacement reactions among halogens. Ideal for students studying chemical bonding and periodic trends.
ChemistryUnderstanding the location and movement of electrons within the atomic structure based on probability maps and orbital regions.
Chemistrythis is the study guide i made for myself for chem this year :) hopefully it helps
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
Yujun Ge
@yujunge_jflh
Atoms and elements are the building blocks of everything around you. Understanding atomic structure helps explain how elements combine to form the world we see. These concepts are foundational to chemistry and will help you make sense of everything from... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Atoms are the smallest units of matter that cannot be broken down by chemical means. Think of atoms as the tiny "LEGO pieces" that build everything you can touch, see, or smell!
Every atom has three main parts working together. At the center is the nucleus, which contains protons (positively charged particles) and neutrons (particles with no charge). Electrons (negatively charged particles) orbit around the nucleus in specific arrangements called energy levels.
The atomic number of an element equals the number of protons in its nucleus. This number determines what element it is! The atomic mass is calculated by adding the protons and neutrons together. In a neutral atom, the number of electrons always equals the number of protons.
Quick Tip: Remember that protons and neutrons live together in the nucleus, while electrons move around outside. The number of protons (atomic number) tells you which element you're looking at!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Electrons aren't just randomly floating around atoms—they organize themselves in specific energy levels (sometimes called shells). Each level has a maximum capacity: the first level holds 2 electrons, the second and third can each hold 8, and the fourth can hold up to 18 electrons.
Elements are pure substances made of only one kind of atom. The number of electrons in a neutral atom always equals its number of protons. This balance keeps the atom electrically neutral (no charge).
When atoms gain or lose electrons, they become ions—particles with an electrical charge. If an atom loses electrons, it becomes a cation with a positive charge . If an atom gains electrons, it becomes an anion with a negative charge. Ions are written with a + or - superscript, like Ca²⁺.
Remember This: You never change the number of protons when forming ions—only electrons move! Losing electrons makes an atom positive, while gaining electrons makes it negative.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Isotopes are variants of the same element with different numbers of neutrons. Think of them as siblings from the same family—same number of protons but different weights because of varying neutron counts. When isotopes are unstable, they're radioactive and undergo decay to reach a more stable form.
The periodic table isn't just a random arrangement of elements—it's organized by increasing atomic number (number of protons). Elements in the same column (group) have the same number of valence electrons, which gives them similar chemical properties. The rows (periods) correspond to the number of electron shells an atom has.
The periodic table is divided into different "blocks" based on which type of orbital is being filled with electrons. This organization helps chemists predict how elements will behave in reactions.
Chemistry Hack: The group number on the periodic table often tells you how many valence electrons an element has—which helps predict how it will bond with other elements!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Valence electrons—the electrons in the outermost energy level—are the key players in forming chemical bonds. Scientists use Lewis dot diagrams to visually represent these valence electrons around element symbols.
There are three major types of bonds that atoms form. Covalent bonds occur when two nonmetal atoms share electron pairs (always an even number like 2, 4, or 6). A simple example is hydrogen gas (H₂), where two hydrogen atoms share their electrons.
Ionic bonds form through electron transfer rather than sharing. When a metal atom gives electrons to a nonmetal atom, the resulting oppositely charged ions attract each other. Sodium chloride (NaCl) is a classic example—sodium gives an electron to chlorine.
Hydrogen bonds are special attractions that form when hydrogen (with a partial positive charge) is attracted to another atom with a negative charge. These bonds might be weaker than the others, but they're crucial for many biological processes!
Bonding Insight: Think of covalent bonds as "sharing" and ionic bonds as "giving and taking." The type of elements involved (metals vs. nonmetals) usually determines which type of bond will form.
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.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Lewis dot structures how to with examples
ChemistryThese notes help inform you on the basics of Chemistry and get you used to the terms used in this subject.
ChemistryAtomic Radius & Ionization Energy
ChemistryExplore the properties, reactivity trends, and bonding characteristics of Group 7 elements (halogens). This summary covers the increasing atomic size, the nature of covalent and ionic bonds, and displacement reactions among halogens. Ideal for students studying chemical bonding and periodic trends.
ChemistryUnderstanding the location and movement of electrons within the atomic structure based on probability maps and orbital regions.
Chemistrythis is the study guide i made for myself for chem this year :) hopefully it helps
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
Algebra
Calculus 1
Algebra 1