7 ms·

Sigma and Pi bonds are typically covered in AP Chemistry, even if the “why/how” is hand waved pretty heavily. The valence cloud shapes get wild for heavier atom

Sigma and Pi bonds are typically covered in AP Chemistry, even if the “why/how” is hand waved pretty heavily. The valence cloud shapes get wild for heavier atoms and bonds between two or more atoms add even more to the mix.

nomel 3mo ago
I had incredible difficulties with Chemistry, more than any other subject, because most everything was hand waved away, requiring mostly rote memorization. I could never get an intuitive understanding, partly because my profs seemingly refusing to think about things from a physics perspective. My physics prof was able to help with some of it. It was very odd. If I would have stuck with it, would things have improved?
- timcobb 3mo ago
  Pi and sigma bonds fall out of thinking of it from a physical/symmetrical/statistical perspective. There's not too much hand waving in the modeling of atomic and molecular orbitals.
- lacunary 3mo ago
  this was my experience as well. "here's a trend, it's not true in these cases for reasons we won't explain." I only had two semesters and the second was much better than the first.
  - ricksunny 3mo ago
    Bronsted-Lowry acids, Lewis dot diagrams - you’re lucky when they tell you that there are any exceptions in the first place, much less actually itemizing some of them.
- ajkjk 3mo ago
  Part of the problem is that the difficulty curve becomes, like, superexponential if you try to do the actual math. Fairly elementary atoms require the full theory of quantum mechanics to justify rigorously, and anything more complicated than that requires huge bodies of specialist knowledge on approximation schemes (I assume; I haven't studied them, but given that helium already requires approximations I'm assuming the trend continues..) Of course, they could still do a much better job useful providing pointers into this knowledge, instead of just handwaving over it and insisting on rote memorization.
  - DiscourseFan 3mo ago
    But oftentimes theoretical chemistry is not as important as what we get out of experiments because unlike physics, which attempts to derive general laws of nature, chemistry has to deal with the nitty gritty of the diversity of actual miscroscopic interactions of things. Any theory that is not entirely rigorous or even has slight room for an exception will be ignored by necessity, and physics is chock full of such examples. Biology is in a certain sense better (since it deals with larger things) and in a certain sense worse (as it relies on dogma and mysticism, at its essence, to explain the systems of life), and still nobody has gone beyond Aristotle and Kant in giving anything close to a rigorous definition of life as such.
    - breezybottom 3mo ago
      [flagged]
    - isomorphic_duck 3mo ago
      how does biology depend on "dogma and mysticism"? I am really curious - a Google search yielded nothing much relevant.
      - AngryData 3mo ago
        I would think just because everything is so cumulatively complicated and interconnected that if you tried to trace a line through a complex biological processes and explain it all you will end up with 1,000 PhD thesis topics to figure out and thousands more you just hadn't noticed yet. And at the end of the day none of that might be all that useful for describing the larger process at work. So at some point when someone ask "Why does X do Y" you gotta just settle on "because that's the way it is" and move on.
      - nemothekid 3mo ago
        I think he's being a little facetious - what he probably means is that if you attempt to get any true scientific rigor of that is going on in biological or chemical systems you end up facing the limits of physics in being able to explain what is going on. So rather and try to have scientific rigor, you just accept things the way they are and memorize the outputs and if anyone asks "why is it like that", your answers are either: * Because God said so * Find out yourself and get a nobel prize Either way, even if you don't know what the answers are, you can still do serious work at a higher level of abstraction.
- aaaronic 3mo ago
  Yes and no. It depends which branch of chemistry you world have chosen to go down. Physical Chemistry certainly improves a fair amount of the hand waving, but even there the underlying physics is simplified fairly often (as I understand it — I went straight Physics and dabbled in Chemistry from the other side).
  - nerdsniper 3mo ago
    As a chemical engineer, one of the signs of maturity was myself and each of my classmates individually coming to accept and embrace the inevitable “magic coefficient”. The curious always wanted to know why some magic coefficient was there. Where did it come from? How is it measured / calculated? How to derive the magic coefficient? Eventually you learn that it’s turtles all the down. You can pick apart the magic coefficient and dive into the nuanced physics that its derived from…but then you still end up with a new magic coefficient. So eventually, the curious students learn that the mysteries are out there for when you want to go out and explore them. But otherwise, we pick our level of abstraction for the problem we’re currently working on and accept the magic coefficients that apply to that level of abstraction. The real trick is knowing the conditional boundaries when those magic coefficients no longed apply and you either need different ones or “here be dragons”.
    - compass_copium 3mo ago
      Are "magic coefficients" not just a result of the units you are using? Like how h-bar is 1 if you are using natural units
      - nine_k 3mo ago
        It's a different kind. Say, some reaction should run 1.23x faster theoretically. But the theory is approximate (in order to be tractable at all), and so are its predictions. This particular element is special in its own way, diverging from the theory a bit, even though its neighbors fit well. That particular bond requires a bit less energy to break than the theory predicts, due to a complex interplay of bonds nearby, understood only qualitatively. Etc, etc. A general theory of everything might describe all of it from first principles, without magic coefficients. But likely computing it would take a decade with current methods.
- abecedarius 3mo ago
  I don't know, I'm not very chemical, but fwiw: a friend and I were favorably impressed with Linus Pauling's general chemistry textbook. It tries to supply enough of the physics for the chemistry to make sense. We only studied for a few weeks before moving on, though, and it's a big fat book.
- ahahs 3mo ago
  that's because chemistry is heavily involved in describing the nature of how elements and molecules interact with each other. There has to be some element of understanding that nothing is quite as clear because we use experiments and their conclusions to slowly but surely eliminate some theories while keeping others until disproven.
- marcosdumay 3mo ago
  The physics that predicts chemistry is about 100 years old. Almost nothing people study up to high-school is that recent, and that modern physics tends to be really hard.
  - deleted 3mo ago
    [deleted]
  - JumpCrisscross 3mo ago
    > physics that predicts chemistry Do we have this?
    - marcosdumay 3mo ago
      You know that people simulate chemistry on computers, right?
      - JumpCrisscross 3mo ago
        Yes. We also simulate cosmology and quantum systems and play Sims.
        marcosdumay 3mo ago
        The difference being that the chemical simulations get the correct answers on most conditions. And probably the few they miss are because of the simulation limitations, not of the underlying model. Those other simulators aren't there to tell you the result. Instead people put the result in to find how the simulation behaves in cosmology, and don't care about them in Sims.
    - gus_massa 3mo ago
      Yes but ... after a few not so mild assumptions, it takes exponential time to solve it. In this case, you need 6 electrons in 2x5 orbitals for the Carbon and 82 electrons and 2x43 orbitals for Bismuth- (perhaps more, I usually work with lighter atom). So now the free parameter are Combinatoric(96,88)~=3E13 and you must construct a matrix of [3E13 x 3E13] and then find the minimal eigenvalue. So you must make a lot of simplifications and more assumptions to get the result before the universe dies. And this is for a very cold isolated molecule like in this experiment. If you have many moving molecules surrounded by a lot of water molecules at a usual room temperature, it gets much much much worse.
- asdff 3mo ago
  Not in undergraduate chemistry at least. Maybe chem majors had it different. Organic chemistry 1 was basically rote memorization of various reactions and catalysts and their required conditions. Exam questions would be some organic molecule start and some organic molecule end result and you'd have to draw out each and every intermediary step to get to that end result. Organic chemistry 2 was exactly the same just more reactions to memorize. Biochem was a little easier since the exams didn't ask for full pathways but still pretty much pure memorization. I hated these sorts off classes, where if you had your notes with you, you'd ace the exam and be able to explain everything. Passing or failing depended not on understanding, but simply whether you cram all the specifics and covered edge cases all into your head at once, given the rest of your present courseload preventing you from actually digging in to the best you could. Wrong answers didn't come from not knowing how to solve something, but not remembering exactly how to solve something.
  - zem 3mo ago
    I was lucky enough to have Morrison and Boyd as my undergrad ochem textbook. they built the material up really well from first principles.
  - compass_copium 3mo ago
    You had a poor organic course. Even orgo 1 should have you thinking about resonance + electron-rich or -deficient areas of molecules and how those lead to reactions.
    - asdff 3mo ago
      Of course we talked about those. But if you went off only those you'd miss the edge cases and gotchas the prof laid for you in step 8 of the synthesis. Couldn't get around just doing worksheet after worksheet after worksheet of reactions to try and drive it into your head. Going to office hours to beg for more practice reactions. Everyone scheduled the rest of their major around when they would have to take ochem to make sure the rest of it was as light as possible. Uncurved class averages would be in the 50s.
- SlightlyLeftPad 3mo ago
  I think this lines up with my experience. The way chemistry is often taught its very abstract, borderline magical. I also had an amazing physics professor who was able to tie literally everything we learned back to real practical and observable events. There is an art to teaching these subjects. This is all undergrad level though, and it wasn’t my major.
- scheme271 3mo ago
  At upper undergrad and grad levels, it probably would have improved a lot. The issue is that a lot of the why requires quantum mechanics to really explain and even that becomes intractable extremely quickly. Like you can probably do the analytic solutions for hydrogen atoms and electrons but once you get to helium or past that, you basically need to use a computer to do numeric calculations and even there, you are very quickly using approximations instead of solving the quantum equations directly.
  - smj-edison 3mo ago
    And also emergent behavior means that at each level, we need different abstractions to deal with the problem. Even with chemistry, there's ideas like benzene rings that are aromatic, that you couldn't predict that from particle-particle interactions. So it's not just that it's hard to understand quantum mechanics, it's that understanding QM doesn't mean you'll understand the problems that chemistry deals with.
    - fc417fc802 3mo ago
      I don't think that's quite right. We only have to worry about emergent behavior precisely because running a full simulation is intractable. If we could "just" run full QM instead of MD with all those lossy force field approximations all the emergent behavior would happen on its own. But obviously doing that is well past science fiction and into the territory of wild fantasy. I think misconceptions commonly arise because there are so many examples where we know how to simulate each part with arbitrary precision but the scale of the system is where it all falls over. That just doesn't match up with our everyday experiences because systems on the scale of avagadros number or O(n^7) algorithms applied to absurdly small timesteps are anything but typical. It's difficult for people to wrap their minds around the implications of having to consider things on nanosecond timescales.
      - smj-edison 3mo ago
        Yes and no. If we could "just" run full QM, there's still the issue of building abstractions regarding the emergent behavior. A full system is still useless if you can't describe things like ligands, carbon rings, etc. So regardless of whether we can simulate it, we still need terms for higher level concepts. But yes, nano and even femtosecond level second stuff is pretty mind bending.
- nsz65 3mo ago
  Yes its like cooking or music. You start just by learning whats in the kitchen and on repeating steps. This creates latent or tacit knowledge that helps with the Why questions down the road.
- whatever1 3mo ago
  We have answers. It’s called physical chemistry. The problem is that it takes a shit ton of math
- jona-f 3mo ago
  Chemistry is very empirical. While we today can explain nearly everything from physics, you still always have check how things will work in experiment, unlike in physic where you often can calculate the outcome of experiments very precisely from first principles. To not have to resort to rote memorization you first have to have the interest. That way you accumulate the knowledge over time, then the patterns feel logical at some point. The logic isn't very precise, maybe that's where you have problems? Some molecules are similar in some molecules in this regard and other molecules in another regard. You will get a feel how stuff behaves. You certainly have a lot of chemistry knowledge you are not aware of. For example, I'm sure you have a good intuition how things burn and you probably know the basics of why it burns. The invisible oxygen in the air is the main chemical insight to explain why stuff burns. You can explain the whole process to whatever detail you like with physics, but many chemists lack the math and physics knowledge to do much of that.
- adastra22 3mo ago
  “Physical chemistry” is the search term for what you’d be interested in. General physics and chemistry take different approaches forced by the subject matter. Physics abstracts to problems over concepts with details abstracted away, but at higher levels of education you learn to apply these corrections. Chemistry starts with practical reality and a lot of rote memorization. Only at the higher levels do you get the unifying theory. Since the unifying theory is quantum electrodynamics (in this case, relativistic QED), that makes sense.
- ahartmetz 3mo ago
  I hated chemistry in school as well for the same reason. I studied physics afterwards... Oddly, once I was looking for information about some experimental physics problem with electron orbitals and found some very well-written theoretical chemistry lecture notes :P
- rramadass 3mo ago
  > If I would have stuck with it, would things have improved? Yes. I have a B.Sc in Chemistry (Honours) from late 1980s and it was not until the final year that things finally began to click. The main catalysts were the books "Concise Inorganic Chemistry by J.D.Lee" and "Mechanism in Organic Chemistry by Peter Sykes". Both beautifully written and try to give a framework within which to think viz. the former based on the periodic table and the latter on carbon valence bond properties. I think i need to revisit these (and other books) to justify my degree in Chemistry :-) For background and inspiration, consult Linus Pauling's classics; The Nature of the Chemical Bond and General Chemistry - https://archive.org/search?query=creator%3A%22Pauling+Linus%22 https://archive.org/search?query=creator%3A%22Pauling+Linus%... Linus Pauling (the only scientist in history to be awarded two undivided, unshared Nobel Prizes) - https://en.wikipedia.org/wiki/Linus_Pauling https://en.wikipedia.org/wiki/Linus_Pauling
- deleted 3mo ago
  [deleted]
- aduty 3mo ago
  No.
- pmarreck 3mo ago
  I had the same issue! I absolutely destroyed AP Physics (first person in the history of the school to get a 5 on the AP and 100 on the NYS Regents) but got a D in AP Chem one semester, my lowest grade ever!!
- nickcw 3mo ago
  One of the disappointing realisations I got from my physics degree was that as you move into the real world with non-spherical cows you can no longer solve any of the equations.
- WillAdams 3mo ago
  The wild thing is that the understanding of electron arrangement made a _huge_ difference in chemistry texts where overnight they went from myriad descriptions of reactions being commented as "...and this is not well understood" to quite thorough and rigorous explanations of chemical interactions.
- K0balt 3mo ago
  Chemistry fundamentally is about producing a result. Physics, especially when you get into particles, is about explaining a result. Ultimately, chemistry, electronics,even civil engineering, is applied physics, but we are a long way from consolidating and closing the gaps. Empirical results stand in for complete understanding in the vast majority of engineering disciplines, both because complete understanding is not needed and also because we don’t have it yet. Fundamentally, chemistry is a variety of engineering discipline, being mostly an applied science.
- dboreham 3mo ago
  The waving, and the resulting need to memorize a zillion special cases, put me off Chemistry for life.
loeg 3mo ago
Granted I took AP Chem 20 years ago, but I don't remember those names (sigma and pi bonds) being covered at all. (I got a 5 on the test, for what it's worth.)
- timcobb 3mo ago
  They are not covered in AP chemistry this is just your typical "when I studied differential geometry in high school" HN comment
  - nosrep 3mo ago
    they are featured in collegeboard's course and exam description: https://apcentral.collegeboard.org/media/pdf/ap-chemistry-course-and-exam-description.pdf https://apcentral.collegeboard.org/media/pdf/ap-chemistry-co...
    - timcobb 3mo ago
      It says, in the document: > Exclusion Statement: Molecular orbital theory is recommended as a way to provide deeper insight into bonding. However, the AP Exam will neither explicitly assess molecular orbital diagrams, filling of molecular orbitals, nor the distinction between bonding, nonbonding, and antibonding orbitals. Orbital theory is usually taught in organic chemistry and then inorganic for those who take that in college. AP chem targets "gen chem" which does not, as the above statement says, does not get into orbitals on that level at all. I'm familiar with gen chem as taught at least in 3 universities, none touched molecular orbitals. If someone were to teach orbital theory in general chemistry, it would be a lot of hand waving and not much actual mathematics which was the point of the original comment. To cover molecular orbital theory is satisfactorily. You need to know quite a bit of the mathematics behind differential equations and statistical mechanics etc. AP chem isn't going to cover this. But maybe your 9th grade differential geometry class covered all this ;))
- compass_copium 3mo ago
  I also took it 20 years ago but I feel like they were (of course I also did undergrad chem 16 years ago so I may be conflating things). It's difficult to explain isomers without explaining why multiple bonds don't rotate.

nomel 3mo ago

I had incredible difficulties with Chemistry, more than any other subject, because most everything was hand waved away, requiring mostly rote memorization. I could never get an intuitive understanding, partly because my profs seemingly refusing to think about things from a physics perspective. My physics prof was able to help with some of it. It was very odd. If I would have stuck with it, would things have improved?

timcobb 3mo ago
Pi and sigma bonds fall out of thinking of it from a physical/symmetrical/statistical perspective. There's not too much hand waving in the modeling of atomic and molecular orbitals.
lacunary 3mo ago
this was my experience as well. "here's a trend, it's not true in these cases for reasons we won't explain." I only had two semesters and the second was much better than the first.
- ricksunny 3mo ago
  Bronsted-Lowry acids, Lewis dot diagrams - you’re lucky when they tell you that there are any exceptions in the first place, much less actually itemizing some of them.
ajkjk 3mo ago
Part of the problem is that the difficulty curve becomes, like, superexponential if you try to do the actual math. Fairly elementary atoms require the full theory of quantum mechanics to justify rigorously, and anything more complicated than that requires huge bodies of specialist knowledge on approximation schemes (I assume; I haven't studied them, but given that helium already requires approximations I'm assuming the trend continues..) Of course, they could still do a much better job useful providing pointers into this knowledge, instead of just handwaving over it and insisting on rote memorization.
- DiscourseFan 3mo ago
  But oftentimes theoretical chemistry is not as important as what we get out of experiments because unlike physics, which attempts to derive general laws of nature, chemistry has to deal with the nitty gritty of the diversity of actual miscroscopic interactions of things. Any theory that is not entirely rigorous or even has slight room for an exception will be ignored by necessity, and physics is chock full of such examples. Biology is in a certain sense better (since it deals with larger things) and in a certain sense worse (as it relies on dogma and mysticism, at its essence, to explain the systems of life), and still nobody has gone beyond Aristotle and Kant in giving anything close to a rigorous definition of life as such.
  - breezybottom 3mo ago
    [flagged]
  - isomorphic_duck 3mo ago
    how does biology depend on "dogma and mysticism"? I am really curious - a Google search yielded nothing much relevant.
    - AngryData 3mo ago
      I would think just because everything is so cumulatively complicated and interconnected that if you tried to trace a line through a complex biological processes and explain it all you will end up with 1,000 PhD thesis topics to figure out and thousands more you just hadn't noticed yet. And at the end of the day none of that might be all that useful for describing the larger process at work. So at some point when someone ask "Why does X do Y" you gotta just settle on "because that's the way it is" and move on.
    - nemothekid 3mo ago
      I think he's being a little facetious - what he probably means is that if you attempt to get any true scientific rigor of that is going on in biological or chemical systems you end up facing the limits of physics in being able to explain what is going on. So rather and try to have scientific rigor, you just accept things the way they are and memorize the outputs and if anyone asks "why is it like that", your answers are either: * Because God said so * Find out yourself and get a nobel prize Either way, even if you don't know what the answers are, you can still do serious work at a higher level of abstraction.
aaaronic 3mo ago
Yes and no. It depends which branch of chemistry you world have chosen to go down. Physical Chemistry certainly improves a fair amount of the hand waving, but even there the underlying physics is simplified fairly often (as I understand it — I went straight Physics and dabbled in Chemistry from the other side).
- nerdsniper 3mo ago
  As a chemical engineer, one of the signs of maturity was myself and each of my classmates individually coming to accept and embrace the inevitable “magic coefficient”. The curious always wanted to know why some magic coefficient was there. Where did it come from? How is it measured / calculated? How to derive the magic coefficient? Eventually you learn that it’s turtles all the down. You can pick apart the magic coefficient and dive into the nuanced physics that its derived from…but then you still end up with a new magic coefficient. So eventually, the curious students learn that the mysteries are out there for when you want to go out and explore them. But otherwise, we pick our level of abstraction for the problem we’re currently working on and accept the magic coefficients that apply to that level of abstraction. The real trick is knowing the conditional boundaries when those magic coefficients no longed apply and you either need different ones or “here be dragons”.
  - compass_copium 3mo ago
    Are "magic coefficients" not just a result of the units you are using? Like how h-bar is 1 if you are using natural units
    - nine_k 3mo ago
      It's a different kind. Say, some reaction should run 1.23x faster theoretically. But the theory is approximate (in order to be tractable at all), and so are its predictions. This particular element is special in its own way, diverging from the theory a bit, even though its neighbors fit well. That particular bond requires a bit less energy to break than the theory predicts, due to a complex interplay of bonds nearby, understood only qualitatively. Etc, etc. A general theory of everything might describe all of it from first principles, without magic coefficients. But likely computing it would take a decade with current methods.
abecedarius 3mo ago
I don't know, I'm not very chemical, but fwiw: a friend and I were favorably impressed with Linus Pauling's general chemistry textbook. It tries to supply enough of the physics for the chemistry to make sense. We only studied for a few weeks before moving on, though, and it's a big fat book.
ahahs 3mo ago
that's because chemistry is heavily involved in describing the nature of how elements and molecules interact with each other. There has to be some element of understanding that nothing is quite as clear because we use experiments and their conclusions to slowly but surely eliminate some theories while keeping others until disproven.
marcosdumay 3mo ago
The physics that predicts chemistry is about 100 years old. Almost nothing people study up to high-school is that recent, and that modern physics tends to be really hard.
- deleted 3mo ago
  [deleted]
- JumpCrisscross 3mo ago
  > physics that predicts chemistry Do we have this?
  - marcosdumay 3mo ago
    You know that people simulate chemistry on computers, right?
    - JumpCrisscross 3mo ago
      Yes. We also simulate cosmology and quantum systems and play Sims.
      - marcosdumay 3mo ago
        The difference being that the chemical simulations get the correct answers on most conditions. And probably the few they miss are because of the simulation limitations, not of the underlying model. Those other simulators aren't there to tell you the result. Instead people put the result in to find how the simulation behaves in cosmology, and don't care about them in Sims.
  - gus_massa 3mo ago
    Yes but ... after a few not so mild assumptions, it takes exponential time to solve it. In this case, you need 6 electrons in 2x5 orbitals for the Carbon and 82 electrons and 2x43 orbitals for Bismuth- (perhaps more, I usually work with lighter atom). So now the free parameter are Combinatoric(96,88)~=3E13 and you must construct a matrix of [3E13 x 3E13] and then find the minimal eigenvalue. So you must make a lot of simplifications and more assumptions to get the result before the universe dies. And this is for a very cold isolated molecule like in this experiment. If you have many moving molecules surrounded by a lot of water molecules at a usual room temperature, it gets much much much worse.
asdff 3mo ago
Not in undergraduate chemistry at least. Maybe chem majors had it different. Organic chemistry 1 was basically rote memorization of various reactions and catalysts and their required conditions. Exam questions would be some organic molecule start and some organic molecule end result and you'd have to draw out each and every intermediary step to get to that end result. Organic chemistry 2 was exactly the same just more reactions to memorize. Biochem was a little easier since the exams didn't ask for full pathways but still pretty much pure memorization. I hated these sorts off classes, where if you had your notes with you, you'd ace the exam and be able to explain everything. Passing or failing depended not on understanding, but simply whether you cram all the specifics and covered edge cases all into your head at once, given the rest of your present courseload preventing you from actually digging in to the best you could. Wrong answers didn't come from not knowing how to solve something, but not remembering exactly how to solve something.
- zem 3mo ago
  I was lucky enough to have Morrison and Boyd as my undergrad ochem textbook. they built the material up really well from first principles.
- compass_copium 3mo ago
  You had a poor organic course. Even orgo 1 should have you thinking about resonance + electron-rich or -deficient areas of molecules and how those lead to reactions.
  - asdff 3mo ago
    Of course we talked about those. But if you went off only those you'd miss the edge cases and gotchas the prof laid for you in step 8 of the synthesis. Couldn't get around just doing worksheet after worksheet after worksheet of reactions to try and drive it into your head. Going to office hours to beg for more practice reactions. Everyone scheduled the rest of their major around when they would have to take ochem to make sure the rest of it was as light as possible. Uncurved class averages would be in the 50s.
SlightlyLeftPad 3mo ago
I think this lines up with my experience. The way chemistry is often taught its very abstract, borderline magical. I also had an amazing physics professor who was able to tie literally everything we learned back to real practical and observable events. There is an art to teaching these subjects. This is all undergrad level though, and it wasn’t my major.
scheme271 3mo ago
At upper undergrad and grad levels, it probably would have improved a lot. The issue is that a lot of the why requires quantum mechanics to really explain and even that becomes intractable extremely quickly. Like you can probably do the analytic solutions for hydrogen atoms and electrons but once you get to helium or past that, you basically need to use a computer to do numeric calculations and even there, you are very quickly using approximations instead of solving the quantum equations directly.
- smj-edison 3mo ago
  And also emergent behavior means that at each level, we need different abstractions to deal with the problem. Even with chemistry, there's ideas like benzene rings that are aromatic, that you couldn't predict that from particle-particle interactions. So it's not just that it's hard to understand quantum mechanics, it's that understanding QM doesn't mean you'll understand the problems that chemistry deals with.
  - fc417fc802 3mo ago
    I don't think that's quite right. We only have to worry about emergent behavior precisely because running a full simulation is intractable. If we could "just" run full QM instead of MD with all those lossy force field approximations all the emergent behavior would happen on its own. But obviously doing that is well past science fiction and into the territory of wild fantasy. I think misconceptions commonly arise because there are so many examples where we know how to simulate each part with arbitrary precision but the scale of the system is where it all falls over. That just doesn't match up with our everyday experiences because systems on the scale of avagadros number or O(n^7) algorithms applied to absurdly small timesteps are anything but typical. It's difficult for people to wrap their minds around the implications of having to consider things on nanosecond timescales.
    - smj-edison 3mo ago
      Yes and no. If we could "just" run full QM, there's still the issue of building abstractions regarding the emergent behavior. A full system is still useless if you can't describe things like ligands, carbon rings, etc. So regardless of whether we can simulate it, we still need terms for higher level concepts. But yes, nano and even femtosecond level second stuff is pretty mind bending.
nsz65 3mo ago
Yes its like cooking or music. You start just by learning whats in the kitchen and on repeating steps. This creates latent or tacit knowledge that helps with the Why questions down the road.
whatever1 3mo ago
We have answers. It’s called physical chemistry. The problem is that it takes a shit ton of math
jona-f 3mo ago
Chemistry is very empirical. While we today can explain nearly everything from physics, you still always have check how things will work in experiment, unlike in physic where you often can calculate the outcome of experiments very precisely from first principles. To not have to resort to rote memorization you first have to have the interest. That way you accumulate the knowledge over time, then the patterns feel logical at some point. The logic isn't very precise, maybe that's where you have problems? Some molecules are similar in some molecules in this regard and other molecules in another regard. You will get a feel how stuff behaves. You certainly have a lot of chemistry knowledge you are not aware of. For example, I'm sure you have a good intuition how things burn and you probably know the basics of why it burns. The invisible oxygen in the air is the main chemical insight to explain why stuff burns. You can explain the whole process to whatever detail you like with physics, but many chemists lack the math and physics knowledge to do much of that.
adastra22 3mo ago
“Physical chemistry” is the search term for what you’d be interested in. General physics and chemistry take different approaches forced by the subject matter. Physics abstracts to problems over concepts with details abstracted away, but at higher levels of education you learn to apply these corrections. Chemistry starts with practical reality and a lot of rote memorization. Only at the higher levels do you get the unifying theory. Since the unifying theory is quantum electrodynamics (in this case, relativistic QED), that makes sense.
ahartmetz 3mo ago
I hated chemistry in school as well for the same reason. I studied physics afterwards... Oddly, once I was looking for information about some experimental physics problem with electron orbitals and found some very well-written theoretical chemistry lecture notes :P
rramadass 3mo ago
> If I would have stuck with it, would things have improved? Yes. I have a B.Sc in Chemistry (Honours) from late 1980s and it was not until the final year that things finally began to click. The main catalysts were the books "Concise Inorganic Chemistry by J.D.Lee" and "Mechanism in Organic Chemistry by Peter Sykes". Both beautifully written and try to give a framework within which to think viz. the former based on the periodic table and the latter on carbon valence bond properties. I think i need to revisit these (and other books) to justify my degree in Chemistry :-) For background and inspiration, consult Linus Pauling's classics; The Nature of the Chemical Bond and General Chemistry - https://archive.org/search?query=creator%3A%22Pauling+Linus%22 https://archive.org/search?query=creator%3A%22Pauling+Linus%... Linus Pauling (the only scientist in history to be awarded two undivided, unshared Nobel Prizes) - https://en.wikipedia.org/wiki/Linus_Pauling https://en.wikipedia.org/wiki/Linus_Pauling
deleted 3mo ago
[deleted]
aduty 3mo ago
No.
pmarreck 3mo ago
I had the same issue! I absolutely destroyed AP Physics (first person in the history of the school to get a 5 on the AP and 100 on the NYS Regents) but got a D in AP Chem one semester, my lowest grade ever!!
nickcw 3mo ago
One of the disappointing realisations I got from my physics degree was that as you move into the real world with non-spherical cows you can no longer solve any of the equations.
WillAdams 3mo ago
The wild thing is that the understanding of electron arrangement made a _huge_ difference in chemistry texts where overnight they went from myriad descriptions of reactions being commented as "...and this is not well understood" to quite thorough and rigorous explanations of chemical interactions.
K0balt 3mo ago
Chemistry fundamentally is about producing a result. Physics, especially when you get into particles, is about explaining a result. Ultimately, chemistry, electronics,even civil engineering, is applied physics, but we are a long way from consolidating and closing the gaps. Empirical results stand in for complete understanding in the vast majority of engineering disciplines, both because complete understanding is not needed and also because we don’t have it yet. Fundamentally, chemistry is a variety of engineering discipline, being mostly an applied science.
dboreham 3mo ago
The waving, and the resulting need to memorize a zillion special cases, put me off Chemistry for life.

loeg 3mo ago

Granted I took AP Chem 20 years ago, but I don't remember those names (sigma and pi bonds) being covered at all. (I got a 5 on the test, for what it's worth.)

timcobb 3mo ago
They are not covered in AP chemistry this is just your typical "when I studied differential geometry in high school" HN comment
- nosrep 3mo ago
  they are featured in collegeboard's course and exam description: https://apcentral.collegeboard.org/media/pdf/ap-chemistry-course-and-exam-description.pdf https://apcentral.collegeboard.org/media/pdf/ap-chemistry-co...
  - timcobb 3mo ago
    It says, in the document: > Exclusion Statement: Molecular orbital theory is recommended as a way to provide deeper insight into bonding. However, the AP Exam will neither explicitly assess molecular orbital diagrams, filling of molecular orbitals, nor the distinction between bonding, nonbonding, and antibonding orbitals. Orbital theory is usually taught in organic chemistry and then inorganic for those who take that in college. AP chem targets "gen chem" which does not, as the above statement says, does not get into orbitals on that level at all. I'm familiar with gen chem as taught at least in 3 universities, none touched molecular orbitals. If someone were to teach orbital theory in general chemistry, it would be a lot of hand waving and not much actual mathematics which was the point of the original comment. To cover molecular orbital theory is satisfactorily. You need to know quite a bit of the mathematics behind differential equations and statistical mechanics etc. AP chem isn't going to cover this. But maybe your 9th grade differential geometry class covered all this ;))
compass_copium 3mo ago
I also took it 20 years ago but I feel like they were (of course I also did undergrad chem 16 years ago so I may be conflating things). It's difficult to explain isomers without explaining why multiple bonds don't rotate.