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Katie
13/12/2025
Chemistry
Chemistry Unit 4- THE PERIODIC TABLE
236
•
13 Dec 2025
•
Mastering Chemistry Unit 4: The Periodic Table
Katie
@katie_hkgy
1 / 4
Periodic Table Basics
Ever wondered why the periodic table looks like a wonky rectangle? It's actually brilliantly organised! Vertical columns are called groups, whilst horizontal rows are called periods.
Here's the clever bit: the group number tells you exactly how many electrons are in the outer shell of each element. Bromine is in group 7, so it has 7 electrons buzzing around its outer shell. The period number shows how many shells of electrons an atom has - bromine is in period 4, so it has 4 shells total.
Atomic size follows a predictable pattern too. As you move across a period from left to right, atoms get smaller. But as you go down a group, they get bigger because they have more electron shells. Think of it like adding more layers to an onion!
Quick Tip: Remember that the atomic number determines the order of elements - it's like their ID number in the periodic table!
Group Trends and Properties
Different groups have totally different personalities! Group 1 elements (like lithium, sodium, and potassium) are called alkali metals - they're the most reactive metals and get more reactive as you go down the group. They all have just 1 electron in their outer shell.
Group 7 elements are the halogens - these are the most reactive non-metals with 7 electrons in their outer shell. But here's the twist: they become less reactive as you go down the group (opposite to Group 1!).
Group 0 (or 8) contains the noble gases - these are the loners of the periodic table. They're completely unreactive because they have full outer shells of electrons, making them perfectly content.
The transition metals sit between groups 2 and 3. They're generally unreactive but form colourful compounds that make chemistry experiments much more interesting!
Memory Trick: Noble gases are "noble" because they don't need to react with anyone - they're already complete!
Metals vs Non-metals and Energy Changes
The periodic table has a clear divide: metals live on the left side, whilst non-metals hang out on the right. As you move across a period, elements change from metallic to non-metallic behaviour. Don't forget that hydrogen is actually a non-metal, even though it sits at the top left!
Some elements like silicon and germanium are semi-metals - they're the rebels that show properties of both metals and non-metals. They can conduct small amounts of electricity, making them perfect for computer chips.
Now let's talk about energy changes in reactions. Exothermic reactions give out heat to their surroundings, making the temperature rise - think of burning wood or hand warmers. Endothermic reactions do the opposite - they absorb heat from their surroundings, causing the temperature to drop, like when ice melts.
Real-world Connection: Your phone's processor uses semi-metal silicon - that's why it gets warm when you're gaming!
The Complete Picture
This visual representation shows how everything fits together perfectly! You can see the alkali metals getting more reactive as you go down Group 1, whilst the halogens become less reactive as you descend Group 7.
The transition metals form that big block in the middle, and you can clearly spot where the dividing line between metals and non-metals runs across the table. The noble gases sit proudly in Group 0, completely unreactive in their perfect stability.
Understanding these patterns means you can predict how elements will behave without memorising every single one. It's like having a cheat code for chemistry - once you know the rules, you can figure out what any element is likely to do!
Exam Success: Learn the group trends and you'll be able to answer questions about elements you've never even heard of!
We thought you’d never ask...
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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
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This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
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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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Mastering Chemistry Unit 4: The Periodic Table
Katie
@katie_hkgy
The periodic table is like a giant map that organises all the chemical elements in a really clever way. Understanding how it works will help you predict how different elements behave and react with each other.
Periodic Table Basics
Ever wondered why the periodic table looks like a wonky rectangle? It's actually brilliantly organised! Vertical columns are called groups, whilst horizontal rows are called periods.
Here's the clever bit: the group number tells you exactly how many electrons are in the outer shell of each element. Bromine is in group 7, so it has 7 electrons buzzing around its outer shell. The period number shows how many shells of electrons an atom has - bromine is in period 4, so it has 4 shells total.
Atomic size follows a predictable pattern too. As you move across a period from left to right, atoms get smaller. But as you go down a group, they get bigger because they have more electron shells. Think of it like adding more layers to an onion!
Quick Tip: Remember that the atomic number determines the order of elements - it's like their ID number in the periodic table!
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Group Trends and Properties
Different groups have totally different personalities! Group 1 elements (like lithium, sodium, and potassium) are called alkali metals - they're the most reactive metals and get more reactive as you go down the group. They all have just 1 electron in their outer shell.
Group 7 elements are the halogens - these are the most reactive non-metals with 7 electrons in their outer shell. But here's the twist: they become less reactive as you go down the group (opposite to Group 1!).
Group 0 (or 8) contains the noble gases - these are the loners of the periodic table. They're completely unreactive because they have full outer shells of electrons, making them perfectly content.
The transition metals sit between groups 2 and 3. They're generally unreactive but form colourful compounds that make chemistry experiments much more interesting!
Memory Trick: Noble gases are "noble" because they don't need to react with anyone - they're already complete!
Sign up to see the contentIt's free!
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Metals vs Non-metals and Energy Changes
The periodic table has a clear divide: metals live on the left side, whilst non-metals hang out on the right. As you move across a period, elements change from metallic to non-metallic behaviour. Don't forget that hydrogen is actually a non-metal, even though it sits at the top left!
Some elements like silicon and germanium are semi-metals - they're the rebels that show properties of both metals and non-metals. They can conduct small amounts of electricity, making them perfect for computer chips.
Now let's talk about energy changes in reactions. Exothermic reactions give out heat to their surroundings, making the temperature rise - think of burning wood or hand warmers. Endothermic reactions do the opposite - they absorb heat from their surroundings, causing the temperature to drop, like when ice melts.
Real-world Connection: Your phone's processor uses semi-metal silicon - that's why it gets warm when you're gaming!
Sign up to see the contentIt's free!
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The Complete Picture
This visual representation shows how everything fits together perfectly! You can see the alkali metals getting more reactive as you go down Group 1, whilst the halogens become less reactive as you descend Group 7.
The transition metals form that big block in the middle, and you can clearly spot where the dividing line between metals and non-metals runs across the table. The noble gases sit proudly in Group 0, completely unreactive in their perfect stability.
Understanding these patterns means you can predict how elements will behave without memorising every single one. It's like having a cheat code for chemistry - once you know the rules, you can figure out what any element is likely to do!
Exam Success: Learn the group trends and you'll be able to answer questions about elements you've never even heard of!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
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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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
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Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
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Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user