Things you never understood in your STEM degree

Basically all the parts in chemistry where 2 atoms bond. I know the theory, but I only know how, not why they bond.

>>7921862
>People who didn't understand things

>why they bond.
I am no chemist but when my high school chem teacher would get asked why certain reactions happen in certain situation he would always give an answer similar to 'nature likes it that way' or 'nature prefers it'.

I think nobody knows. It's like asking why are the laws of physics like that.

>noncommutative geometry
>twistor theory
>modular forms
>female sexuality

>>7921866
It's energetically favourable. That's it. It's why things bond, it's why things decay, etc.

>>7921883
But why? Why can't be the other way around? Why don't we live in an inneficient universe that just likes to concentrate energy and tends to that..

>>7921889
I don't know anon, but we're just a minus sign away.

[math]F = -\frac{\mathrm{d} U}{\mathrm{d}r}[/math]

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>>7921862
>quantum mechanics

>>7921862

miller indices are not that hard to understand man come on

>>7921895
what's a dudr?

>>7921997
drrrrdrrrrr

>>7921866
lol and the charge of atoms

"so x is positive and y is negative"

"why sir?"

>>7921997

https://youtu.be/bJ8q3wAjYvM?t=23s

Chemistry is quite abstract until you learn the reasons behind it desu

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>>7921889
On a microscopic scale that is what happens.
When your system settles into a low energy state, it doesn't have enough energy to get out. Over time the random jiggling finds itself in such a local minimum of energy and becomes stuck - the thermal motion isn't energetic enough to escape the low energy state. That's why some chemical reactions require heat to get them going - you need to supply energy to get the system out of the slump.
There's more to it that this, especially on the level of individual atoms and molecules since these are quantum objects and classical reasoning does not apply, but the basic idea is that everything happens randomly, and over time this random motions tends to push towards certain states - the low energy ones.

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>>7921866
>>7921869
>>7921889
>>7921883
one of the better theories tee be etch

OP did you read your books at all or just rely on lectures/notes?

most undergrad physics books do a good job at explaining most of that stuff

>>7922363
>tee be etch
Aitch.

>>7922386
ayytch

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FUCK OFF WITH YOUR FUCKING FERMI SPHERES REEEE

>Probabilistic coupling
Too bad, it sounded very elegant too but I never could make it work on paper.

>>7921866
Ask a chemist what a bond even is. We deal with bonds all the time, yet it's not even that easy to answer.

the goldbach conjecture

what does it mean in the long run

>>7921862
> Impact Testing
> Fatigue limits
> Euler's Bending Equation apparently
> clearly I don't understand thermo very well either

Stats and probability, beyond tremendously basic shit. Took an intro class and never used it afterwards in my work/field of research, so I forgot everything.

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related rates in calc 1

thank god that shit never showed up in calc 2 or anything else

>>7923925
this

>tfw math tutor
>tfw 99% of students want tutoring on stats and probability shit

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>>7921862
>quantum mechanics of a 1D well

if you don't get that, how did you ever learn about time independent perturbations ?

Fucking Lagrangian mechanics.

>>7921862
>>Feynman diagrams
THIS

>>7924005

I didn't. I failed quantum and took a philosophy of science course instead.

Tensors
I mean, I get things like the inertia tensor, but the math and index manipulation never stick with me.

>>7921862
So you didn't understand the whole of first year? Did you drop out?

>>7922277
More electrons than protons (each bonding electron counts as one electron for each involved atom)

>>7921866
>>7921869
>>7921883
>>7921889
>>7922277
>>7922314

The problem is no one believes the real answer for why there are bonds, and they can't handle it either.

The truth is that the electron wave function of one atom interferes with the electron wave function on the other atom. If they are out of phase, they destructively interfere and form a higher energy non bonding orbital which just means there is lower probability of finding electrons between the atoms.

However, If they constructively interfere the probability density between both atoms adds and forms a lower energy orbital where electrons are more likely to be found. Since electrons are more likely to be found there, the positive nuclei are attracted to it. There only has to be one electron for this to happen.

This is exactly the same case as the double slit experiment. The electron wave function of an electron that goes through one slit interferes with the electron wave function that goes through the other slit.

A bond is where a single electron's probability of being on one atom constructively interferes with its own probability of being on the other atom.

Modern chemistry uses this reasoning through molecular orbital theory to predict actual reactions all the time; as a concrete example check out Woodward-Hoffman rules:

https://en.wikipedia.org/wiki/Woodward%E2%80%93Hoffmann_rules

>>7924175
It's so cute when little underage kids post on 4chan to show off how they got a 4 on the AP physics C exam. Fuck off. /sci/ isn't for your huge fucking ego, nigger

>>7921862
>Feynman diagrams
I can help with this.

Watch These:
http://pirsa.org/C14037/1
http://pirsa.org/C14034


Great shit for learning QFT.