Biology
Chemistry
AP Chemistry
English
AP English Literature
Chemistry
Dec 3, 2025
50
5 pages
Aysha ๐ @ayshaahmed_hqen
The periodic table is chemistry's ultimate cheat sheet - it organises all known elements in a way that... Show more
Dmitri Mendeleev created the periodic table by arranging elements into groups (columns) and periods (rows). Elements in the same group share similar chemical properties, which is why they're grouped together.
Originally, elements were arranged by increasing mass, but we now organise them by atomic number (the number of protons). This updated system makes much more sense and eliminates the gaps Mendeleev had to leave.
Quick Tip Remember that groups go down and periods go across - just like reading a book!
Alkali metals are the show-offs of the periodic table - they react dramatically with water! Lithium fizzes gently, sodium melts into a ball with an orange flame, and potassium puts on the biggest display with a lilac flame.
These metals become more reactive as you move down the group. All alkali metals have one electron in their outer shell, which explains why they're so eager to react.
The pattern is clear lithium (2,1), sodium (2,8,1), and potassium (2,8,8,1) all share that single outer electron. This makes them incredibly useful for predicting chemical behaviour.
Remember Group 1 = 1 outer electron = very reactive metals that love water!
Alkaline earth metals are group 2's reactive metals, though less dramatic than their group 1 neighbours. Magnesium produces small bubbles in water, whilst calcium fizzes more vigorously and forms white powder.
Halogens are group 7's reactive non-metals with seven electrons in their outer shell. Unlike alkali metals, halogens become less reactive as you move down the group.
Fluorine sits at the top as the most reactive halogen. This opposite trend to group 1 shows how the periodic table reveals fascinating patterns across different element families.
Key Pattern Group 1 gets more reactive going down, Group 7 gets less reactive going down!
Transition metals occupy the middle section of the periodic table and don't follow the usual group numbering system. They're incredibly useful as catalysts - substances that speed up reactions without being consumed.
These metals form coloured compounds, which explains why many paints, dyes, and gemstones contain transition metals. Think copper's blue-green colour or iron's rusty red.
Noble gases are the complete opposite - they're unreactive because they have full outer shells of electrons. This makes them stable and reluctant to form compounds with other elements.
Memory Trick Noble gases are "noble" because they don't mix with common elements - just like snobbish nobility!
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 โ all at your fingertips.
0
Smart Tools NEW
Transform this note into: โ 50+ Practice Questions โ Interactive Flashcards โ Full Mock Exam โ Essay Outlines
Notes on the periodic table, atoms, elements, and more
ChemistryExplains periodic properties of each of the elements
ChemistryYuther foyd's groundbreaking experiment with gold foil reveals small, positively charged particles and their impact on atomic structure.
ChemistryExplore the fundamentals of atomic structure and the periodic table in this comprehensive summary. Key concepts include atomic composition, isotopes, ions, and the development of the periodic table by Mendeleev and Newlands. Ideal for students preparing for exams, this resource features clear explanations and a simplified mind map for better understanding.
ChemistryNotes about the history and arrangement of the elements on the periodic table
ChemistryLists the 5 states of matter, how they can be defined when split, and introduces the parts of the symbols/labels on the Periodic Table
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 itโs very much worth it and youโll 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 donโt get it!!! In the end I think itโs worth it ๐๐ โ ๏ธAlso DID I MENTION ITS FREEE YOU DONโT HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLYโ๏ธโ๏ธโ ๏ธ
Thomas R
iOS user
Knowunity is the BEST app Iโve 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 help๐ค๐ค
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.๐๐ฉท๐
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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 Iโve 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 itโs very much worth it and youโll 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 donโt get it!!! In the end I think itโs worth it ๐๐ โ ๏ธAlso DID I MENTION ITS FREEE YOU DONโT HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLYโ๏ธโ๏ธโ ๏ธ
Thomas R
iOS user
Knowunity is the BEST app Iโve 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 help๐ค๐ค
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.๐๐ฉท๐
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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 Iโve seen! Geometry too!
Paul T
iOS user
Aysha ๐
@ayshaahmed_hqen
The periodic table is chemistry's ultimate cheat sheet - it organises all known elements in a way that reveals patterns and helps predict how they'll behave. Understanding how Russian chemist Dmitri Mendeleev arranged elements by their properties will unlock the... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Dmitri Mendeleev created the periodic table by arranging elements into groups (columns) and periods (rows). Elements in the same group share similar chemical properties, which is why they're grouped together.
Originally, elements were arranged by increasing mass, but we now organise them by atomic number (the number of protons). This updated system makes much more sense and eliminates the gaps Mendeleev had to leave.
Quick Tip: Remember that groups go down and periods go across - just like reading a book!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Alkali metals are the show-offs of the periodic table - they react dramatically with water! Lithium fizzes gently, sodium melts into a ball with an orange flame, and potassium puts on the biggest display with a lilac flame.
These metals become more reactive as you move down the group. All alkali metals have one electron in their outer shell, which explains why they're so eager to react.
The pattern is clear: lithium (2,1), sodium (2,8,1), and potassium (2,8,8,1) all share that single outer electron. This makes them incredibly useful for predicting chemical behaviour.
Remember: Group 1 = 1 outer electron = very reactive metals that love water!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Alkaline earth metals are group 2's reactive metals, though less dramatic than their group 1 neighbours. Magnesium produces small bubbles in water, whilst calcium fizzes more vigorously and forms white powder.
Halogens are group 7's reactive non-metals with seven electrons in their outer shell. Unlike alkali metals, halogens become less reactive as you move down the group.
Fluorine sits at the top as the most reactive halogen. This opposite trend to group 1 shows how the periodic table reveals fascinating patterns across different element families.
Key Pattern: Group 1 gets more reactive going down, Group 7 gets less reactive going down!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Transition metals occupy the middle section of the periodic table and don't follow the usual group numbering system. They're incredibly useful as catalysts - substances that speed up reactions without being consumed.
These metals form coloured compounds, which explains why many paints, dyes, and gemstones contain transition metals. Think copper's blue-green colour or iron's rusty red.
Noble gases are the complete opposite - they're unreactive because they have full outer shells of electrons. This makes them stable and reluctant to form compounds with other elements.
Memory Trick: Noble gases are "noble" because they don't mix with common elements - just like snobbish nobility!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
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 โ all at your fingertips.
0
Smart Tools NEW
Transform this note into: โ 50+ Practice Questions โ Interactive Flashcards โ Full Mock Exam โ Essay Outlines
Notes on the periodic table, atoms, elements, and more
ChemistryExplains periodic properties of each of the elements
ChemistryYuther foyd's groundbreaking experiment with gold foil reveals small, positively charged particles and their impact on atomic structure.
ChemistryExplore the fundamentals of atomic structure and the periodic table in this comprehensive summary. Key concepts include atomic composition, isotopes, ions, and the development of the periodic table by Mendeleev and Newlands. Ideal for students preparing for exams, this resource features clear explanations and a simplified mind map for better understanding.
ChemistryNotes about the history and arrangement of the elements on the periodic table
ChemistryLists the 5 states of matter, how they can be defined when split, and introduces the parts of the symbols/labels on the Periodic Table
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 itโs very much worth it and youโll 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 donโt get it!!! In the end I think itโs worth it ๐๐ โ ๏ธAlso DID I MENTION ITS FREEE YOU DONโT HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLYโ๏ธโ๏ธโ ๏ธ
Thomas R
iOS user
Knowunity is the BEST app Iโve 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 help๐ค๐ค
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.๐๐ฉท๐
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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 Iโve 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 itโs very much worth it and youโll 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 donโt get it!!! In the end I think itโs worth it ๐๐ โ ๏ธAlso DID I MENTION ITS FREEE YOU DONโT HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLYโ๏ธโ๏ธโ ๏ธ
Thomas R
iOS user
Knowunity is the BEST app Iโve 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 help๐ค๐ค
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.๐๐ฉท๐
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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 Iโve seen! Geometry too!
Paul T
iOS user
