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Updated Apr 15, 2026
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Kemijske Molekule in Njihove Oblike
1 / 7
Osnove oblik molekul
Predstavljaj si molekule kot majhne 3D skulpture, ne kot ploščate risbe. Oblika molekule neposredno vpliva na to, ali se bo snov topila v vodi, kakšno bo imela vrelišče in kako bo reagirala z drugimi snovmi.
VSEPR teorija je tvoj glavni pripomoček za razumevanje oblik. Ime zveni zapleteno, a princip je preprost: elektroni se med seboj odbijajo, ker so vsi negativno nabiti. Zato se elektronski pari okoli centralnega atoma razporedijo čim dlje narazen.
Centralni atom je tisti, na katerega se veže največ drugih atomov - okrog njega gradimo celotno obliko. Vezni elektronski pari tvorijo kovalentne vezi, prosti elektronski pari pa so "samski" elektroni, ki zavzamejo več prostora.
💡 Ključno za razumevanje: Prosti elektronski pari so kot "debeli" sosedje - potrebujejo več prostora in potiskajo druge pare skupaj!
Tu pride najbolj zanimiv del: polarnost molekule ni odvisna le od polarnih vezi, ampak tudi od oblike! Simetrična molekula je lahko nepolarna kljub polarnim vezem.
VSEPR teorija in osnovne oblike
Določitev oblike molekule je kot sestavljanka s štirimi koraki. Najprej narišeš Lewisovo strukturno formulo, določiš centralni atom, prešteješ elektronske pare in izbereš ustrezno obliko.
Moč odboja med elektronskimi pari ni enaka - prosti pari odbijajo najstrejše, nato prosto-vezni, najšibkeje pa vezni-vezni. Zato prosti pari "stisnejo" vezi skupaj in zmanjšajo kote.
Osnovno tabelo oblik molekul si zapomni s primeri:
- Linearna (180°): CO₂, BeCl₂
- Trigonalno planarna (120°): BF₃, SO₃
- Tetraedrična (109,5°): CH₄, CCl₄
- Trigonalno piramidalna (~107°): NH₃, PCl₃
- Kotna (~104,5°): H₂O, H₂S
💡 Pomni: Več prostih parov = manjši koti med vezmi!
Opazi, kako se koti zmanjšujejo: metan ima idealen kot 109,5°, amonijak 107°, voda pa le 104,5°. To je posledica vse močnejšega odboja prostih parov.
Praktični primeri z rešitvami
Metan (CH₄) je tvoj osnovni primer. Ogljik v sredini, štirje vodiki okrog njega. Štirje vezni pari, nič prostih - rezultat je tetraedrična oblika s koti 109,5°.
Kljub rahlo polarnim C-H vezem je molekula nepolarna, ker je popolnoma simetrična. Težišče pozitivnega in negativnega naboja je na istem mestu.
Amonijak (NH₃) je drugačen. Dušik ima tri vodike in en prosti elektronski par. Ta prosti par "potisne" tri vezi skupaj, nastane trigonalno piramidalna oblika s kotom 107°.
💡 Test trick: NH₃ je polarna, ker prosti par na vrhu uniči simetrijo!
Voda (H₂O) ima dva prosta para, ki še močneje stisneta dve vezi. Nastane kotna oblika s kotom 104,5°. Ker je asimetrična in ima polarne O-H vezi, je zelo polarna molekula.
Ključne razlike za test
Ne zamenjaj polarne vezi in polarne molekule! Polarna vez nastane med atomoma z različno elektronegativnostjo. Polarna molekula pa mora biti še asimetrična.
CCl₄ je odličen primer: ima štiri polarne C-Cl vezi, a je molekula nepolarna zaradi tetraedrične simetrije. Učinki se izničijo.
Postopek za teste:
- Nariši pravilno Lewisovo strukturo
- Določi centralni atom
- Preštej vezne in proste pare
- Izberi obliko iz tabele
- Preveri simetrijo za polarnost
💡 Za najboljšo oceno: Vedno najprej preveri simetrijo, šele nato sklepaj o polarnosti!
Hiter pregled oblik: linearna (ravna črta), trigonalno planarna (ploščat trikotnik), tetraedrična (piramida s triangularno osnovo), trigonalno piramidalna (piramida z enim prostim parom), kotna (ukrivljena kot bumerang).
Zapomni si: simetrične molekule so nepolarne (CH₄, CO₂, BF₃), asimetrične pa polarne (H₂O, NH₃, HCl).
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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 Knowunity AI. 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 Knowunity AI. 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
Kemijske Molekule in Njihove Oblike
Zakaj je pomembno vedeti, kako so molekule oblikovane? Ker oblika določa, kako se snovi obnašajo - od tega, ali se olje meša z vodo, do tega, kako delujejo zdravila v telesu. Molekule namreč niso ploščate slike iz učbenikov, ampak tridimenzionalne... Show more
Osnove oblik molekul
Predstavljaj si molekule kot majhne 3D skulpture, ne kot ploščate risbe. Oblika molekule neposredno vpliva na to, ali se bo snov topila v vodi, kakšno bo imela vrelišče in kako bo reagirala z drugimi snovmi.
VSEPR teorija je tvoj glavni pripomoček za razumevanje oblik. Ime zveni zapleteno, a princip je preprost: elektroni se med seboj odbijajo, ker so vsi negativno nabiti. Zato se elektronski pari okoli centralnega atoma razporedijo čim dlje narazen.
Centralni atom je tisti, na katerega se veže največ drugih atomov - okrog njega gradimo celotno obliko. Vezni elektronski pari tvorijo kovalentne vezi, prosti elektronski pari pa so "samski" elektroni, ki zavzamejo več prostora.
💡 Ključno za razumevanje: Prosti elektronski pari so kot "debeli" sosedje - potrebujejo več prostora in potiskajo druge pare skupaj!
Tu pride najbolj zanimiv del: polarnost molekule ni odvisna le od polarnih vezi, ampak tudi od oblike! Simetrična molekula je lahko nepolarna kljub polarnim vezem.
Sign up to see the contentIt's free!
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VSEPR teorija in osnovne oblike
Določitev oblike molekule je kot sestavljanka s štirimi koraki. Najprej narišeš Lewisovo strukturno formulo, določiš centralni atom, prešteješ elektronske pare in izbereš ustrezno obliko.
Moč odboja med elektronskimi pari ni enaka - prosti pari odbijajo najstrejše, nato prosto-vezni, najšibkeje pa vezni-vezni. Zato prosti pari "stisnejo" vezi skupaj in zmanjšajo kote.
Osnovno tabelo oblik molekul si zapomni s primeri:
- Linearna (180°): CO₂, BeCl₂
- Trigonalno planarna (120°): BF₃, SO₃
- Tetraedrična (109,5°): CH₄, CCl₄
- Trigonalno piramidalna (~107°): NH₃, PCl₃
- Kotna (~104,5°): H₂O, H₂S
💡 Pomni: Več prostih parov = manjši koti med vezmi!
Opazi, kako se koti zmanjšujejo: metan ima idealen kot 109,5°, amonijak 107°, voda pa le 104,5°. To je posledica vse močnejšega odboja prostih parov.
Sign up to see the contentIt's free!
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Improve your grades
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Praktični primeri z rešitvami
Metan (CH₄) je tvoj osnovni primer. Ogljik v sredini, štirje vodiki okrog njega. Štirje vezni pari, nič prostih - rezultat je tetraedrična oblika s koti 109,5°.
Kljub rahlo polarnim C-H vezem je molekula nepolarna, ker je popolnoma simetrična. Težišče pozitivnega in negativnega naboja je na istem mestu.
Amonijak (NH₃) je drugačen. Dušik ima tri vodike in en prosti elektronski par. Ta prosti par "potisne" tri vezi skupaj, nastane trigonalno piramidalna oblika s kotom 107°.
💡 Test trick: NH₃ je polarna, ker prosti par na vrhu uniči simetrijo!
Voda (H₂O) ima dva prosta para, ki še močneje stisneta dve vezi. Nastane kotna oblika s kotom 104,5°. Ker je asimetrična in ima polarne O-H vezi, je zelo polarna molekula.
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Ključne razlike za test
Ne zamenjaj polarne vezi in polarne molekule! Polarna vez nastane med atomoma z različno elektronegativnostjo. Polarna molekula pa mora biti še asimetrična.
CCl₄ je odličen primer: ima štiri polarne C-Cl vezi, a je molekula nepolarna zaradi tetraedrične simetrije. Učinki se izničijo.
Postopek za teste:
- Nariši pravilno Lewisovo strukturo
- Določi centralni atom
- Preštej vezne in proste pare
- Izberi obliko iz tabele
- Preveri simetrijo za polarnost
💡 Za najboljšo oceno: Vedno najprej preveri simetrijo, šele nato sklepaj o polarnosti!
Hiter pregled oblik: linearna (ravna črta), trigonalno planarna (ploščat trikotnik), tetraedrična (piramida s triangularno osnovo), trigonalno piramidalna (piramida z enim prostim parom), kotna (ukrivljena kot bumerang).
Zapomni si: simetrične molekule so nepolarne (CH₄, CO₂, BF₃), asimetrične pa polarne (H₂O, NH₃, HCl).
Sign up to see the contentIt's free!
Access to all documents
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Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
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?
You can download the app from Google Play Store and 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.
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4.6/5
App Store
4.7/5
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 Knowunity AI. 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 Knowunity AI. 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