9.5 Molecular Orbital Theory | General Chemistry

Chad provides a comprehensive lesson on Molecular Orbital Theory. The lesson begins by showing how overlap of atomic orbitals results in both bonding and antibonding molecular orbitals. Constructive overlap between atomic orbitals results in a lower energy, bonding molecular orbital, while destructive overlap between atomic orbitals results in a higher energy, antibonding molecular orbital. The Molecular Orbital diagrams of H2 and He2 are both presented and used to explain why H2 exists and He2 does not. It is also shown how to calculate bond order from a molecular orbital diagram (formula) and how for many species this is consistent with the number of bonds in the Lewis structure.
The Molecular Orbital diagrams for homonuclear diatomic molecules of the second period are then presented. The Molecular Orbital diagrams of O2, F2, and Ne2 are presented and the corresponding bond orders calculated. Paramagnetic and diamagnetic are defined and it is shown that a species is paramagnetic if it has unpaired electrons and diamagnetic if all of its electrons are paired. The MO diagrams are then used to explain why Ne2 does not exist (bond order = 0) and why O2 is paramagnetic, something that wouldn't be predicted by the Lewis structure. The MO diagram for N2 is then presented and it is shown that the energies of the sigma 2p and pi 2p molecular orbitals are inverted due to sp mixing in the MO diagram for Li2, Be2, B2, C2, and N2. The bond order for N2 is calculated (it equals 3) which corresponds nicely with the triple bond present in the Lewis structure.
I've embedded this playlist as a course on my website with all the lessons organized by chapter in a collapsible menu and much of the content from the study guide included on the page. Check this lesson out at www.chadsprep.com/chads-gener...
If you want all my study guides, quizzes, final exam reviews, and practice exams, check out my General Chemistry Master Course (free trial available) at www.chadsprep.com/genchem-you...
00:00 Lesson Introduction
01:09 Constructive & Destructive Overlap
05:26 Sigma 1s & 1s*
14:30 Sigma 2p & 2p*
19:58 Pi 2p & 2p*
24:34 Molecular Orbital Diagram for H2
26:29 Molecular Orbital Diagram for He2
27:17 How to Calculate Bond Order from Molecular Orbital Diagram
30:58 Molecular Orbital Diagram for O2, F2, Ne2
35:22 Paramagnetic vs Diamagnetic
39:54 Molecular Orbital Diagram for N2
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[@sumnerjones8588]

teaching is an art, and this video instruction is honestly comparable to a Monet water lily; Chad explains it to us like we are students, not scientists. That is a strangely simple, yet commonly misunderstood pedagogy many instructors miss. Awesome stuff, Chad! Thanks :)

[@ChadsPrep]

You are gracious in your comparison. You're welcome and thank you.

[@fdrisgreat]

Honestly, you should teach college professors how to teach chemistry, o chem or any science course in plain English terms.

[@ChadsPrep]

Kind words - thank you very much.

[@anthonybwalya139]

They’re lecturers. They don’t teach. They lecture.

[@Ahyawnah]

@@anthonybwalya139then they’re not necessary tbh

[@anthonybwalya139]

@@Ahyawnah they teach adults not kids. An adult can be lectured coz they can comprehend on their own.

[@sk.iftekharulislam3678]

This has been the BEST class on Molecular Orbital Theory, from covering all the basic visualizations and understandings and then taking up all the corresponding concepts.... Sir, you should start teaching courses on "How to Teach" I can't be anymore grateful, thanks a ton for such informative and structured Lecture....Bless you!!

[@ChadsPrep]

Thank you for your kind words - glad the channel is helping you!

[@mariasalloua]

Not all heros wear capes and this man right here is an absolute example

[@ChadsPrep]

Thanks - kind words.

[@Mikikkk28]

I watched all your videos since 2017 and last year I was able to start working as a TA for the chem department!!! All thanks to you Chad

[@ChadsPrep]

Excellent, SK - much success to you!

[@aminulislamishmam5607]

one of the best lectures I have ever seen. This topic has always been extremely unclear to me for YEARS, and you have finally been able to make sense of it for me. Amazing! Also the production quality and sound are top notch

[@ChadsPrep]

Glad the video/channel is helping you - Happy Studying!

[@CC-mk1sv]

Hands down the BEST explanation of MO theory on youtube!! Thank you for explaining this. I have a midterm coming up in a few days and I was struggling so much to understand this theory during review, but now I am much more confident. Thank YOU!

[@ChadsPrep]

You're welcome - Glad to hear it. Hope you do well on your midterm.

[@ines12moavro13]

Incredibly helpful. Really good and intuitive explanations, not just technicalities. A huge thank you, Chad!

[@ChadsPrep]

You're welcome and a huge Thank You back!

[@adamchao1187]

Hey, I'm just randomly reviewing for my gen chem class, but I just wanted to say thank you so much for these videos. You're able to explain things so clearly, it's almost like magic. I'm always struggling in class trying to understand what the professor is saying but I'm never worried because I have these videos to fall back on. Truly, thank you!.

[@ChadsPrep]

You're welcome and Thank You!

[@lavis7933]

SAVED MY LIFE. ive been struggling with MO theory and MO diagrams and these videos were REALLY helpful. i understood everything omg A HUGE THANK YOU

[@ChadsPrep]

You're welcome!

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i've been watching you since the start of this semester and you have helped me sooo much, thank you!!

[@ChadsPrep]

Glad the channel is helping you - Happy Studying!

[@nourlahrichi590]

I’ve been struggling with this for 2 days and he just makes it so much easier. Thank you

[@ChadsPrep]

You're welcome.

[@foxyfrog]

I found your channel while looking for an explanation about MO theory, and I am so happy I know about your videos now! The way you explain things makes it so easy to understand. I started studying this semester for my BA/MS in Biochemistry and I'm so excited I have your videos to help me along the way. Thank you so much for your time and effort making these videos, it is greatly appreciated!

[@ChadsPrep]

Glad you found us - Happy Studying!

[@stevenchen2567]

Such positive vibes and extremely clear visualization to help students understand the material. One of the best videos I've seen on the internet, fantastic!

[@ChadsPrep]

Thanks Steven! You might also want to check out a recent video on the same topic: kzbin.info/www/bejne/pYjdpqSCoZt8qtE Dr. Robertson and his team included some great illustrations and animations; really well done!

[@kmichelle6728]

I'm a medical student all over in South Korea, was having a hard time cramming for my general chemistry final exam. I was doubting watching this video because all the other videos I watched were either too deep or only too shallow...but well, turns out to be the best choice before my exam. I excelled at the exam :)

[@ChadsPrep]

Kudos on your exam performance - glad you found us!

[@giannispappas663]

Thank you for sharing these lectures, the examples/practice questions are incredibly helpful!

[@ChadsPrep]

You're welcome - glad to hear it!

[@Oluwasefunmi_Peace]

I just have to subscribe now. Thanks a lot Chad. Your video on R and S configuration helped me a lot and I was very happy to see your video pop up few minutes ago as I was looking for videos to help me understand Molecular Orbitals.

[@ChadsPrep]

Awesome to hear it and welcome to the channel :)

[@adhip0574]

Simply amazing, thanks for getting me up to speed on my AP chem class!

[@ChadsPrep]

You are most welcome.

[@jeannine2483]

It's amazing that molecules bond and stay together with all of this wonderful complexity.

[@ChadsPrep]

Amazing, indeed!

[@MKLee369]

Thanks for your videos about atomic orbitals and molecular orbitals! 👍These topics are generally more abstract and thus difficult than other topics in general chemistry, but you explains much more clearly than my professor. I had just finished my midterm covering these topics, and I score 49/50 (50 MCQs, mean = 31)! 😆You save my grade! 😄Without your teaching, I definitely cannot get such high score!

[@ChadsPrep]

Glad the channel is helping you out!

[@seyoummisgana2824]

I would like to express my greatest admiration!!! Precise and clear explanation thanks alot.

[@ChadsPrep]

You're welcome and Thank you very much.

[@user-vk9yh7to3t]

A HUGE THANK YOU! I am currently studying for my test tomorrow and your video is really the best!

[@ChadsPrep]

A huge you're welcome - hope you do well on your test!

[@jennymurphy23]

Thank you so much for this lecture and video! It has been instrumental to grasping MOT!

[@ChadsPrep]

You are most welcome.

[@user-qt1qh7zl6k]

Hey!! Great explanation, very helpful! Also, did you make a video on Heteronuclear compounds' MO diagram?

[@silver9883]

Holy cow thank you so much for simplifying this! I feel so much better about my final tomorrow !!!

[@ChadsPrep]

Glad the video helped - Hope you do well on your final!

[@user-bq9wg9mv7e]

Thank you for saving my grade and for making this concept genuinely interesting and possible to learn

[@ChadsPrep]

You're welcome - glad it helped you out!

[@marriakhan2989]

one of the best channels for learning chemistry.

[@ChadsPrep]

Thank you!

[@AlexanderGilling]

Thisi is such a good video, and his name is CHAD. Chad chem video absolutely destroys my prof chem lectures (as in he does way better at explaining everything). underrated neeeds more subs.

[@ChadsPrep]

Kind words - thank you. Glad for YOUR sub and Happy Studying!

[@AshtamiManoj]

Thank you so much! This video was so helpful to clear my doubts of MOT.

[@ChadsPrep]

You're welcome - Glad to hear it!

[@margodphd]

Three Twentysix recommended me Your lectures and I'm very thankful. You are an excellent teacher. You truly are the Chaddiest of Chemistry Chads ❤

[@ChadsPrep]

Thanks so much! Welcome to the channel :)

[@Rosy2026]

you are amazing, I was stuck in this subject, and now I understand better, thank you!!

[@ChadsPrep]

That's great to hear - You're welcome and Thank You.

[@lindagrace5065]

I wish I could like this video more than once. It helped a lot, Thank you so much.

[@ChadsPrep]

Appreciate your kind words, Linda!

[@realcirno1750]

This is the best video of molecular orbitals on the internet.

[@ChadsPrep]

Thank you.

[@AreciaKhova]

This has been really helpful, thank you so much🙏

[@ChadsPrep]

You're welcome - Glad to hear it!

[@adrijaghosh8780]

Thanks alot man!! You make complicated stuffs easy pizzy!! Also, a special thanks to KZbin algorithm for suggesting me your channel. You are really making life of chemistry students easy.. Thanks real life Heisenberg a.k.a walter white 😌... Love and respect from India 🇮🇳

[@ChadsPrep]

You are welcome and Thank you - Happy Studying from USA!

[@blinkybit]

I'm a post grad. chem student and I'm making connections with Chad's vids that I haven't been able to with yrs of hoity-toity profs. lecturing 😋 bloody legend!

[@ChadsPrep]

Glad to hear it, Josh - Happy Studying!

[@venkinta3343]

I'm an Aerospace engineering student. I find myself having basic chem as a course and I haven't had a chem class in two years. This video has helped me a bunch, I hope it manages to get me to pass chem so i never have to deal with it again!

[@ChadsPrep]

Glad you found the channel - Happy Studying!

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Thank you so much, I can’t believe I have accidentally come across such a good channel!

[@ChadsPrep]

Glad you did - Happy Studying!

[@louegebaguio170]

I've been watching your videos since I was in college. And right now, I am also a chemistry lecturer. Thanks chad! Hope to connect with you!

[@ChadsPrep]

Awesome to hear this :)

[@silvermist6891]

Thank you so much. I finally understand MOT now!

[@ChadsPrep]

That's great!

[@saii221]

extremely helpful, I appreciate this channel a lot💜. It would be amazing if you'd make follow ups to go more in depth with the lectures

[@ChadsPrep]

Thank you.

[@user-in8fb5iq6y]

Thank you so much. I learnt a lot from this KZbin video.

[@ChadsPrep]

You're welcome - Glad to hear it!

[@user-sm4ol1sl6s]

Best video about MOT. Thank you soooo much this video helped me a lot🙏

[@ChadsPrep]

Awesome! You are welcome :)

[@onespace4712]

The way our teacher taught us man! 'i was really confused and didn't understand much' but now thanks to you sir everything is like crystal clear and this lesson might give me an edge on my competitive exam.

[@ChadsPrep]

Glad to hear it - hope you do well on your exam.

[@onespace4712]

@@ChadsPrep I have a doubt sir the B.O.(He2)=0 this concludes it forms no bond that's why (He2) doesn't exist but B.O.(Be2) =0 then how does Beryllium forms a dimer and exist.

[@ChadsPrep]

Great question. Molecular orbital theory doesn't predict stable dimers for beryllium or for the noble gases as discussed in the video. But weakly bonded dimers exist not only for beryllium, but for noble gases also! From the perspective of molecular orbital theory, this was completely unexpected. It has been accounted for with some advanced quantum mechanics and the interactions are more like van der Waals forces than covalent bonds. Hope this helps!

[@annelisegertrud9546]

Thank you so much for explaining so good 🙏🏽🙏🏽

[@ChadsPrep]

You are most welcome.

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Thank you. Very clear explanation and helpful video

[@ChadsPrep]

Great to hear, Matilde!

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I've never seen any teacher like I love you chad❤

[@ChadsPrep]

Glad the channel is helping!

[@user-ti9vx9lj3i]

God bless you Chad!! This is an amazing video

[@ChadsPrep]

Thank you and to you as well.

[@BrianOSheaPlus]

Thanks, this is a great refresher for me, as I haven't studied MO theory in over 28 years (I don't work in the Chemistry field).

[@ChadsPrep]

Glad it helped - Happy Studying!

[@KAlicaya]

thank you so much i learned how to do these diagrams incredibly fast I am truly thankful for this video!!!

[@ChadsPrep]

Glad it helped!

[@enochthomaz8334]

This is the most informative video on molecular orbital theory.

[@ChadsPrep]

Thank you

[@Grateful92]

Came here from three twentysix, and, really got benefited by your video. Thank you too 🙏

[@ChadsPrep]

Glad it is helpful!

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[@ChadsPrep]

Glad the videos are helping you!

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I really appreciate you for making this. Very helpful to all university students.

[@ChadsPrep]

You're welcome and Thank You.

[@kimarthurmandia4011]

You're a great mentor.

[@ChadsPrep]

Thank you.

[@maddycoo]

this so was so so so helpful, thanks chad!😊

[@ChadsPrep]

Glad to hear it - You're welcome.

[@reemmasri9274]

beautiful explanation. Thank you!

[@ChadsPrep]

You're welcome and Thank You!

[@Quackadillyblip27]

This was just what i needed THANKS

[@ChadsPrep]

Glad the channel helped you out!

[@paarmyida]

Best teacher to teach chemistry out there

[@ChadsPrep]

Thank you

[@user-qi9ub9uf3m]

It was really helpful. Thanks a million 🙏

[@ChadsPrep]

You're very welcome.

[@user-zn9xr9fy9m]

MARVELOUS explanation, 2 hours before midterm

[@ChadsPrep]

Thank you

[@AasiyahAtobajaye-jh6dk]

This was soo helpful Thanks a lot👍👍

[@ChadsPrep]

Very welcome!

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you are saving me, I wish university would hire ACTUAL teachers to teach these courses, would make things a lot easier. I have my final exam in 2 days and going through everyone one of your gen chem videos has solidified my understanding SO much more. I wish I found these videos earlier, I will absolutely be posting your page in the discord for this course! Here's to hoping I pass and dont need to retake it in spring lol!

[@ChadsPrep]

All the best on your final - Thanks and Happy Studying!

[@veden3383]

at my uni the chemistry teachers have kind of given up, they regurgitate the same unintuitive powerpoints year after year. I also have the exam in two days. Best of luck to you

[@ChadsPrep]

How did the exam go?

[@veden3383]

@@ChadsPrep I failed. Mine was harder than before, they asked things in roundabout ways. I knew too little of the specifics. I also dislike their exams since they can ask for the lewis model for R-CHx for example, but then in the exam answer afterwards, they always go on long tangents that aren't specifically asked for.

[@adamchao1187]

truly a chad 🙏 - thank you

[@ChadsPrep]

You're welcome

[@julietohagwa8926]

Thank You so much for this class!

[@ChadsPrep]

You're welcome.

[@angelomanfredini1993]

Hi from Italy. Very wonderful lesson.

[@ChadsPrep]

Hello and Thank you from USA.

[@sarah246.]

amazing explanation, I am really speechless I watched a lot of videos on this concept but did not understand until I came across your video. (Btw I am class 10)❤❤

[@ChadsPrep]

Thanks and Welcome to the channel - Happy Studying!

[@hermine6004]

thank youuuu so much. this was very helpful :))

[@ChadsPrep]

You're so welcome!

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I was really stressed about it i have the finals coming and inglish is my second language, but surprisingly i understood all of them. Thank you so much you helped me alot i was starting to loose hope and I'm glad that i didn't ❤thank you❤

[@ChadsPrep]

Great to hear this :) Good luck on your finals!

[@christinechikoti2243]

Helped a lot thank you 😊

[@ChadsPrep]

Very welcome!

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I'm from Egypt and i loved your explanation ❤❤

[@ChadsPrep]

Thank you from USA!

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You’re just so good❤❤❤❤❤

[@ChadsPrep]

Thank you

[@user-hg7ls2jg1g]

I have a question 😊 Does the MO diagram works for the 3rd raw of periodic table or just the two first raws ?

[@florentinosanchez3969]

Thank you so much for making it

[@ChadsPrep]

You're welcome

[@noormabdullah]

Wow. well explained

[@ChadsPrep]

Thank you

[@user-cx2py2qq4g]

i haven't seen any clearer than this thank u

[@ChadsPrep]

You're welcome - thank you.

[@agries.melisses_edits4538]

Thanks a lot!! Is there a video for heteronuclear molecules, such as CO or NO, because I get confused in that part...

[@Omni-Kriss]

Great video once again!

[@ChadsPrep]

Thanks, Omni-Kriss - glad you like the videos!

[@helinabdulla6831]

Well, teacher, to make the diagram that we say [1s2 2s2 2p3 ] should we make the last two levels of the diagram or for all three? Because you did it in one example for two. The other is all three?

[@DaiyanMao]

You are the god of chem

[@ChadsPrep]

Glad the channel is helping you.

[@yashkumar9671]

very helpful, thanks a lot.

[@ChadsPrep]

You're welcome and Thank You.

[@Elxa-fb5gv]

Very helpful😊❤

[@ChadsPrep]

Glad to hear it!

[@knutritter461]

In our QM-lectures we never depicted 'common' oxygen like O=O because that would be suitable for diamagnetic singulett-oxygen. Better ways for paramagnetic triplett-oxygen we used were •O-O• or with the two dots between the Os above the sigma-bond. Maybe even like O÷O Greetings from an M. Sc. in chemistry.

[@user-ir6uq6ln3i]

You just saved my chem grade, thank you very much

[@ChadsPrep]

You're welcome - Glad you found us.

[@samkhani2147]

Thank you so much sir

[@ChadsPrep]

Very welcome.

[@Deathcorp297]

Does the structure change for every type of bonding and is it always the same?

[@user-py3kv4dt2y]

Wow! I listened to countless lectures and was failing to understand this complex subject! I understand it perfectly after watching this video! Thankyou so much, Chad!

[@ChadsPrep]

That's great to hear :)

[@Mayorrode]

bless you sir!

[@ChadsPrep]

Thank you

[@TheBigBanggggg]

Start here: 1:10

[@sami-sk1bu]

THANK YOU I OWE YOU BIG TIME

[@ChadsPrep]

You're welcome.

[@dilant3258]

How they define orbital energy levels? By computational calculations? like DFT?

[@joe_ninety_one5076]

Very approachable. Amazingly good actually, as I followed it all and I'm not even a chemist. I did physics and maths, dropping chemistry quite early on. Two nitpicks: In the first few minutes the term mathematical 'equation' was used instead of 'function'. At 26:22 it is stated that processes tend to minimise the energy of the universe. It is more a question of maximising the entropy of the universe. Energy is conserved. The decrease in molecular energy has to be reflected by an increase in the energy of the rest of the universe. Entropy, though, is not conserved and increases when energy is distributed throughout the whole universe. These momentary remarks are very much a side issue here and do not detract at all from the value of this video.

[@user-gq7lg5oi6i]

Thank you so much

[@ChadsPrep]

You are most welcome.

[@florentinosanchez3969]

Really nice video

[@ChadsPrep]

Glad you liked it.

[@user-hg7ls2jg1g]

Perfect really really thank you 💕💕

[@ChadsPrep]

You're welcome and Thank You!

[@HappyIsMe159]

2024 and you are still blessing students with your knowledge and help. Thank you so so much for your patience and clarity in teaching a difficult subject!!!

[@ChadsPrep]

You're welcome and Thank You!

[@pangoliff1932]

Thanks Chad

[@ChadsPrep]

You're welcome! :)

[@yichern2376]

thankyou so much prof

[@ChadsPrep]

You are welcome - Happy Studying.

[@etb_27]

When looking at O2, we see there is one sigma bond and one pi bond when you draw the lewis structure. I'm confused as to why there is a second set of sigma orbitals (σ2p and σ2p*) since there is only one sigma bond. Shouldn't there only be σ2s, σ2s*, π2p, π2p*, and one bonding, unhybridized p orbital along with one antibonding, unhybridized p orbital?

[@royhutchinson457]

thanks... helps...

[@ChadsPrep]

Glad to hear.