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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
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2d religious conflict and the church in england, c1529-c1570
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1c the tudors: england, 1485-1603
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Chemistry
4 Dec 2025
380
4 pages
Katie Rose @katierose
Transition metals are the workhorses of chemistry - they're everywhere from the coins in your pocket to the... Show more
Transition metals sit between groups 2 and 3 on the periodic table and are called d-block elements because they have an incomplete d subshell in at least one of their ions. This is what gives them their special properties that other metals just don't have.
Most d orbitals fill up following the normal aufbau principle, but chromium and copper are rebels - they break the rules because having a half-filled or completely filled d subshell is more stable. When these metals form ions, they always lose their 4s electrons first, not the 3d ones.
Oxidation states are basically how many electrons an atom has gained or lost when it's part of a compound. Transition metals are brilliant because they can have multiple oxidation states, which explains why they form compounds with different colours.
Quick Tip Remember that oxidation numbers in a neutral compound always add up to zero - this is your go-to check when working out oxidation states!
Working out oxidation numbers is actually straightforward once you know the rules. Elements on their own are always zero, single-atom ions equal their charge, oxygen is usually -2, and hydrogen is usually +1.
Transition metals can exist in different oxidation states within their compounds, and this flexibility makes them incredibly useful. High oxidation states often make compounds that are oxidising agents, while low oxidation states tend to create reducing agents.
The stability of different oxidation states depends on electronic structure, bonding type, and stereochemistry. This is why some oxidation states are more common than others for each metal.
Remember Oxidation = increase in oxidation number, Reduction = decrease in oxidation number. OIL RIG still works!
Ligands are electron donors that attach to transition metal ions to form coordination compounds or complexes. Think of them as molecules or ions with lone pairs of electrons that can form coordinate bonds with the metal.
Ligands are classified by how many bonds they can form - monodentate (one bond), bidentate (two bonds), up to hexadentate (six bonds). The coordination number tells you how many bonds the central metal ion has to ligands, which determines the shape of the complex.
Naming complexes follows specific rules that might seem complicated at first, but they're logical. You write ligands alphabetically, add prefixes for multiples (di, tri, tetra), and change endings for negative ion ligands to end in 'o'. Common ligands like water become 'aqua' and ammonia becomes 'ammine'.
Pro Tip The formula goes in square brackets with the overall charge outside - this makes it clear what's part of the complex!
The amazing colours of transition metal complexes come from d-d transitions. When ligands approach the metal ion, they split the d orbitals into different energy levels. Electrons can jump between these levels when they absorb light energy.
The spectrochemical series ranks ligands by their ability to split d orbitals. Strong field ligands like CN⁻ cause large energy gaps, while weak field ligands like I⁻ cause smaller gaps. You see the complementary colour to whatever's absorbed.
Transition metals make excellent catalysts because of their variable oxidation states and available d orbitals. Heterogeneous catalysts are in a different state to reactants, whilst homogeneous catalysts are in the same state. Both work by providing alternative reaction pathways with lower activation energies.
Key Point Catalyst poisoning happens when substances bind irreversibly to active sites, so industrial processes need to be carefully controlled!
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Explore the fundamentals of oxidation and reduction in this detailed summary. Understand key concepts such as oxidizing and reducing agents, oxidation states, and electronegativity. Ideal for A-Level chemistry students preparing for exams, this resource covers essential redox reactions and their applications in various compounds.
ChemistryExplore key concepts in transition metals, periodicity, and group trends with this comprehensive summary. Understand oxidation states, catalytic properties, complex ion formation, and the reactivity of groups 2 and 7. Ideal for AQA A-Level chemistry students seeking to enhance their understanding of the periodic table and related chemical reactions.
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
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
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
Katie Rose
@katierose
Transition metals are the workhorses of chemistry - they're everywhere from the coins in your pocket to the catalysts that make industrial processes possible. These d-block elements have some seriously cool properties that make them stand out from other metals,... Show more
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Transition metals sit between groups 2 and 3 on the periodic table and are called d-block elements because they have an incomplete d subshell in at least one of their ions. This is what gives them their special properties that other metals just don't have.
Most d orbitals fill up following the normal aufbau principle, but chromium and copper are rebels - they break the rules because having a half-filled or completely filled d subshell is more stable. When these metals form ions, they always lose their 4s electrons first, not the 3d ones.
Oxidation states are basically how many electrons an atom has gained or lost when it's part of a compound. Transition metals are brilliant because they can have multiple oxidation states, which explains why they form compounds with different colours.
Quick Tip: Remember that oxidation numbers in a neutral compound always add up to zero - this is your go-to check when working out oxidation states!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Working out oxidation numbers is actually straightforward once you know the rules. Elements on their own are always zero, single-atom ions equal their charge, oxygen is usually -2, and hydrogen is usually +1.
Transition metals can exist in different oxidation states within their compounds, and this flexibility makes them incredibly useful. High oxidation states often make compounds that are oxidising agents, while low oxidation states tend to create reducing agents.
The stability of different oxidation states depends on electronic structure, bonding type, and stereochemistry. This is why some oxidation states are more common than others for each metal.
Remember: Oxidation = increase in oxidation number, Reduction = decrease in oxidation number. OIL RIG still works!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ligands are electron donors that attach to transition metal ions to form coordination compounds or complexes. Think of them as molecules or ions with lone pairs of electrons that can form coordinate bonds with the metal.
Ligands are classified by how many bonds they can form - monodentate (one bond), bidentate (two bonds), up to hexadentate (six bonds). The coordination number tells you how many bonds the central metal ion has to ligands, which determines the shape of the complex.
Naming complexes follows specific rules that might seem complicated at first, but they're logical. You write ligands alphabetically, add prefixes for multiples (di, tri, tetra), and change endings for negative ion ligands to end in 'o'. Common ligands like water become 'aqua' and ammonia becomes 'ammine'.
Pro Tip: The formula goes in square brackets with the overall charge outside - this makes it clear what's part of the complex!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The amazing colours of transition metal complexes come from d-d transitions. When ligands approach the metal ion, they split the d orbitals into different energy levels. Electrons can jump between these levels when they absorb light energy.
The spectrochemical series ranks ligands by their ability to split d orbitals. Strong field ligands like CN⁻ cause large energy gaps, while weak field ligands like I⁻ cause smaller gaps. You see the complementary colour to whatever's absorbed.
Transition metals make excellent catalysts because of their variable oxidation states and available d orbitals. Heterogeneous catalysts are in a different state to reactants, whilst homogeneous catalysts are in the same state. Both work by providing alternative reaction pathways with lower activation energies.
Key Point: Catalyst poisoning happens when substances bind irreversibly to active sites, so industrial processes need to be carefully controlled!
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
6
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the fundamentals of oxidation and reduction in this detailed summary. Understand key concepts such as oxidizing and reducing agents, oxidation states, and electronegativity. Ideal for A-Level chemistry students preparing for exams, this resource covers essential redox reactions and their applications in various compounds.
ChemistryExplore key concepts in transition metals, periodicity, and group trends with this comprehensive summary. Understand oxidation states, catalytic properties, complex ion formation, and the reactivity of groups 2 and 7. Ideal for AQA A-Level chemistry students seeking to enhance their understanding of the periodic table and related chemical reactions.
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
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
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
Sociology