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15
0
K
kkm_
9/9/2025
Chemistry
C4 Predicting & Identifying Reactions & Products: Combined science
490
•
Sep 9, 2025
•
Discover the Physical and Chemical Properties of Group 1 Alkali Metals and Group 7 Halogens
K
kkm_
@kkm_
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Alkali Metal Reactions with Water
The observations of alkali metals reactions with water become more vigorous down Group 1:
- Lithium: Floats with some fizzing, produces alkaline solution
- Sodium: Floats, melts, and moves vigorously across surface
- Potassium: Floats, splits, explodes with lilac flame
- Rubidium: Sinks, sparks vigorously, produces flame
- Caesium: Very explosive, breaks container, produces flame
Example: Rubidium + water → rubidium hydroxide + hydrogen 2Rb + 2H₂O → 2RbOH + H₂ (g)
Alkali metals also react with oxygen in air to form metal oxides:
4M + O₂ (g) → 2M₂O (s)
Definition: Oxidation reaction - A reaction in which a substance combines with oxygen
Group 7 Halogens
The properties of Group 7 elements (halogens) include:
- Non-metallic properties: brittle, dull solids, poor conductors
- Diatomic molecules with weak intermolecular forces
- Seven electrons in outermost shell
- Form covalent bonds and 1- ions (halide ions) in reactions
Trends and properties in Group 7 halogens down the periodic table:
- Colors become darker
- Reactivity and bleaching effect decrease
- Density increases
- Melting and boiling points increase
Vocabulary: Diatomic - Consisting of two atoms
Example: The diatomic halogens are F₂, Cl₂, Br₂, and I₂
Halogen Properties and Reactivity
The physical properties of Group 7 elements vary:
- Fluorine and chlorine: Gases at room temperature
- Bromine: Liquid at room temperature
- Iodine and astatine: Solids at room temperature
Chemical properties of Group 7:
- React with metals to form ionic metal halides
- React with non-metals to form covalent compounds
- React with hydrogen to form hydrogen halides
Highlight: Fluorine is the most reactive halogen due to its small size and strong electron-attracting ability.
The trend in reactivity of Group 7 decreases down the group as it becomes harder for larger atoms to gain electrons.
Example: Chlorine can displace bromine from potassium bromide solution, demonstrating its higher reactivity.
Halogen Displacement Reactions
Halogen displacement reactions occur when a more reactive halogen displaces a less reactive halogen from an aqueous solution. This demonstrates the trend in reactivity down Group 7.
For example:
- Chlorine can displace bromine from potassium bromide
- Chlorine can displace iodine from potassium iodide
- Bromine can displace iodine from potassium iodide
Definition: Displacement reaction - A reaction where a more reactive element takes the place of a less reactive element in a compound
These reactions provide evidence for the decreasing reactivity trend in Group 7 elements.
Group 1 Alkali Metals
The physical properties of alkali metals in Group 1 include being soft, low density, and having relatively low melting and boiling points. They are shiny when freshly cut and good conductors of electricity and heat.
Key chemical properties of Group 1 alkali metals:
- Form alkaline solutions when reacting with water
- Have one electron in outermost shell
- Increase in reactivity down the group
- Form 1+ ions when reacting
- Number of electron shells increases down group
Example: The general equation for alkali metals reacting with water is: 2M + 2H₂O → 2MOH + H₂ (g)
Highlight: Alkali metals must be stored in oil to prevent reaction with oxygen and water vapor in air.
Vocabulary: Alkalinity - The property of being alkaline or basic (pH greater than 7)
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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.
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Brad T
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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
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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
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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
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
Discover the Physical and Chemical Properties of Group 1 Alkali Metals and Group 7 Halogens
K
kkm_
@kkm_
Group 1 alkali metals and Group 7 halogens exhibit distinct trends in their physical and chemical properties across the periodic table. Key points include:
- Alkali metals increase in reactivity down Group 1 due to weaker attraction between outer electrons and... Show more
Alkali Metal Reactions with Water
The observations of alkali metals reactions with water become more vigorous down Group 1:
- Lithium: Floats with some fizzing, produces alkaline solution
- Sodium: Floats, melts, and moves vigorously across surface
- Potassium: Floats, splits, explodes with lilac flame
- Rubidium: Sinks, sparks vigorously, produces flame
- Caesium: Very explosive, breaks container, produces flame
Example: Rubidium + water → rubidium hydroxide + hydrogen 2Rb + 2H₂O → 2RbOH + H₂ (g)
Alkali metals also react with oxygen in air to form metal oxides:
4M + O₂ (g) → 2M₂O (s)
Definition: Oxidation reaction - A reaction in which a substance combines with oxygen
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Group 7 Halogens
The properties of Group 7 elements (halogens) include:
- Non-metallic properties: brittle, dull solids, poor conductors
- Diatomic molecules with weak intermolecular forces
- Seven electrons in outermost shell
- Form covalent bonds and 1- ions (halide ions) in reactions
Trends and properties in Group 7 halogens down the periodic table:
- Colors become darker
- Reactivity and bleaching effect decrease
- Density increases
- Melting and boiling points increase
Vocabulary: Diatomic - Consisting of two atoms
Example: The diatomic halogens are F₂, Cl₂, Br₂, and I₂
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Halogen Properties and Reactivity
The physical properties of Group 7 elements vary:
- Fluorine and chlorine: Gases at room temperature
- Bromine: Liquid at room temperature
- Iodine and astatine: Solids at room temperature
Chemical properties of Group 7:
- React with metals to form ionic metal halides
- React with non-metals to form covalent compounds
- React with hydrogen to form hydrogen halides
Highlight: Fluorine is the most reactive halogen due to its small size and strong electron-attracting ability.
The trend in reactivity of Group 7 decreases down the group as it becomes harder for larger atoms to gain electrons.
Example: Chlorine can displace bromine from potassium bromide solution, demonstrating its higher reactivity.
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Halogen Displacement Reactions
Halogen displacement reactions occur when a more reactive halogen displaces a less reactive halogen from an aqueous solution. This demonstrates the trend in reactivity down Group 7.
For example:
- Chlorine can displace bromine from potassium bromide
- Chlorine can displace iodine from potassium iodide
- Bromine can displace iodine from potassium iodide
Definition: Displacement reaction - A reaction where a more reactive element takes the place of a less reactive element in a compound
These reactions provide evidence for the decreasing reactivity trend in Group 7 elements.
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Group 1 Alkali Metals
The physical properties of alkali metals in Group 1 include being soft, low density, and having relatively low melting and boiling points. They are shiny when freshly cut and good conductors of electricity and heat.
Key chemical properties of Group 1 alkali metals:
- Form alkaline solutions when reacting with water
- Have one electron in outermost shell
- Increase in reactivity down the group
- Form 1+ ions when reacting
- Number of electron shells increases down group
Example: The general equation for alkali metals reacting with water is: 2M + 2H₂O → 2MOH + H₂ (g)
Highlight: Alkali metals must be stored in oil to prevent reaction with oxygen and water vapor in air.
Vocabulary: Alkalinity - The property of being alkaline or basic (pH greater than 7)
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We thought you’d never ask...
What is the Knowunity AI companion?
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.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
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Essay
Can't find what you're looking for? Explore other subjects.
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4.8/5
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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
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