Biology
Chemistry
AP Chemistry
English
AP English Literature
Chemistry
Nov 29, 2025
138
2 pages
Dive into the fascinating world of periodic trends where you'll discover how atomic properties change as you move... Show more
Ever wonder why atoms change size across the periodic table? Atomic radius (half the distance between identical atoms in a molecule) follows predictable patterns. As you move across a period, radii generally decrease because electrons are added to the same energy level while proton count increases, pulling electrons closer. Moving down a group, radii increase because electrons enter higher energy levels, farther from the nucleus.
When atoms become ions, size changes dramatically. Ionic radius measures the size of an ion. Metals tend to form positive cations (losing electrons and becoming smaller), while nonmetals form negative anions (gaining electrons and becoming larger). Going across a period, both cation and anion radii decrease, but there's a significant size jump when switching from cations to anions.
Transition metals don't follow the typical patterns. As you move across transition metals in a period, the d sublevel fills, causing atomic radii to decrease slightly before increasing. Cation sizes vary without a consistent trend.
💡 Think of it like this Across a period, the nucleus pulls electrons harder (smaller atoms), while down a group, you're adding new "floors" to the electron "apartment building" (larger atoms).
Ionization energy reveals how tightly atoms hold their electrons. It's the energy needed to remove an electron from a gaseous atom or ion. First ionization energy generally increases across periods and decreases down groups. This happens because electrons are closer to the nucleus across a period but farther away down a group.
Imagine atoms as being either eager or reluctant to accept new electrons. Electron affinity measures this tendency as the energy required to add an electron to a neutral gaseous atom. When an atom readily accepts electrons, the electron affinity is more negative (energy is released). This value becomes more negative across a period as atoms get closer to completing their outer shell. Moving down a group, electron affinity becomes less negative as valence electrons are farther from the nucleus.
Electronegativity is all about electron-grabbing power in chemical bonds. It measures how strongly an atom attracts electrons from another atom in a compound. The trend is straightforward electronegativity increases across a period (except for noble gases in group 18) and decreases down a group. This happens for the same reasons as other periodic trends – across a period, increasing nuclear charge pulls electrons more strongly, while down a group, electrons are farther from the nucleus.
💡 Think of electronegativity like a game of tug-of-war for electrons. Elements on the upper right of the periodic table (like fluorine and oxygen) are the strongest players, while elements on the bottom left (like cesium) have the weakest pull.
Understanding these trends helps predict chemical behavior. Elements with high electronegativity values often form bonds by taking electrons from elements with low electronegativity, creating ionic compounds that are essential in everything from table salt to batteries.
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
Explore the key groups of the periodic table, including Alkali Metals (Group 1), Alkaline Earth Metals (Group 2), Halogens (Group 7), Noble Gases (Group 8), and Transition Metals. This summary highlights their reactivity, electron configurations, and historical development by Dmitri Mendeleev.
ChemistryExplains periodic properties of each of the elements
ChemistryNotes about the history and arrangement of the elements on the periodic table
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.
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 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
Dive into the fascinating world of periodic trends where you'll discover how atomic properties change as you move across or down the periodic table. Understanding these patterns makes chemistry more predictable and helps explain why elements behave the way they... Show more
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Improve your grades
Join milions of students
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Ever wonder why atoms change size across the periodic table? Atomic radius (half the distance between identical atoms in a molecule) follows predictable patterns. As you move across a period, radii generally decrease because electrons are added to the same energy level while proton count increases, pulling electrons closer. Moving down a group, radii increase because electrons enter higher energy levels, farther from the nucleus.
When atoms become ions, size changes dramatically. Ionic radius measures the size of an ion. Metals tend to form positive cations (losing electrons and becoming smaller), while nonmetals form negative anions (gaining electrons and becoming larger). Going across a period, both cation and anion radii decrease, but there's a significant size jump when switching from cations to anions.
Transition metals don't follow the typical patterns. As you move across transition metals in a period, the d sublevel fills, causing atomic radii to decrease slightly before increasing. Cation sizes vary without a consistent trend.
💡 Think of it like this: Across a period, the nucleus pulls electrons harder (smaller atoms), while down a group, you're adding new "floors" to the electron "apartment building" (larger atoms).
Ionization energy reveals how tightly atoms hold their electrons. It's the energy needed to remove an electron from a gaseous atom or ion. First ionization energy generally increases across periods and decreases down groups. This happens because electrons are closer to the nucleus across a period but farther away down a group.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Imagine atoms as being either eager or reluctant to accept new electrons. Electron affinity measures this tendency as the energy required to add an electron to a neutral gaseous atom. When an atom readily accepts electrons, the electron affinity is more negative (energy is released). This value becomes more negative across a period as atoms get closer to completing their outer shell. Moving down a group, electron affinity becomes less negative as valence electrons are farther from the nucleus.
Electronegativity is all about electron-grabbing power in chemical bonds. It measures how strongly an atom attracts electrons from another atom in a compound. The trend is straightforward: electronegativity increases across a period (except for noble gases in group 18) and decreases down a group. This happens for the same reasons as other periodic trends – across a period, increasing nuclear charge pulls electrons more strongly, while down a group, electrons are farther from the nucleus.
💡 Think of electronegativity like a game of tug-of-war for electrons. Elements on the upper right of the periodic table (like fluorine and oxygen) are the strongest players, while elements on the bottom left (like cesium) have the weakest pull.
Understanding these trends helps predict chemical behavior. Elements with high electronegativity values often form bonds by taking electrons from elements with low electronegativity, creating ionic compounds that are essential in everything from table salt to batteries.
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
Explore the key groups of the periodic table, including Alkali Metals (Group 1), Alkaline Earth Metals (Group 2), Halogens (Group 7), Noble Gases (Group 8), and Transition Metals. This summary highlights their reactivity, electron configurations, and historical development by Dmitri Mendeleev.
ChemistryExplains periodic properties of each of the elements
ChemistryNotes about the history and arrangement of the elements on the periodic table
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.
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 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
