HF

A silly little blog where I post about my silly little studies :)

[hydroflouricacid]

✨ Intro Post ✨

I'm Rain, a chemistry student! I'll be posting my various successes (and frequent failures) here.

I'm not using this blog to try and make myself study more or so forth, because that just doesn't work for me. I don't have goals (aside from... passing) and I try to take a more chill approach to my studies.

[rain-clouds-and-autumn-leaves]

Oh also i follow/like from @rain-clouds-and-autumn-leaves :)

[hartsnkises]

Alan Turing and Ada of Lovelace did not invent computer science for the girls and the gays to claim they can't do math

[erbiumspectrum]

This was revealed to me last night as I was falling asleep and I decided I needed to inflict this on you guys as well

[erbiumspectrum]

9 June 2026 🌥️

I finished the conference poster today!! Oof. I thought I'd never arrange it. It isn't "done" done bc it still needs my thesis supervisor's approval, but until Monday - which is when I'm seeing him - I consider it done

I'm giving the very last presentation of the semester tomorrow and therefore wrapping up the silica project :) No more SEM I think, at least not in the foreseeable future

Left pic is all the material for this Friday's exam. I honestly don't know how to go about studying for it bc I have absolutely no idea what to expect 🫪 The professor is unpredictable

Currently reading A Room with a View; I didn't know it was this funny! I'm enjoying it a lot, definitely going to read more Forster

[memories]

My body is but a #study temple.

[memories]

Sally sells #scienceblr by the sea shore.

[memories]

I’ve been silent for too long and can no longer bear to keep this inside: @erbiumspectrum is a good person and deserves many good things.

[sobcat]

I gave her a textbook so I'm not studying alone

[sorcery-and-socialism]

[erbiumspectrum]

Here's a bit of a bonus to my post on selection rules.

[via]

On the left you can see a solution of Mn^(2+) ions. It is pretty much colorless. You can find photos where there is some coloration - pale pink it is often called - but even then it's barely there. On the right is an MnO4^- solution, and believe me, those are even more brilliant irl. (And don't even get me started on solid KMnO4. When powdered, it's as if you are holding the night sky in your hands- Sorry. Let's get back to the post.)

Why are these two so different?

Manganese is a d-block element. Like I said in the post linked above, d-d transitions are forbidden by the Laporte rule. Electrons shrug and say, "Fuck the Laporte rule and also Laporte and his entire family!!!" But not so fast! The ground state of the Mn^(2+) ion has a spin multiplicity of 6. What's a spin multiplicity? Don't worry about it kitten To put it very simply, it tells us about the total spin of the system. And funnily enough, the ground state is the only state of the Mn^(2+) ion that has such a stupid spin multiplicity. This means that basically all electronic transitions in this ion are forbidden: not only parity-forbidden but also spin-forbidden.

And now shit got serious. With two selection rules holding up the stop sign, the probability that electrons will find a way around them reduces greatly. No light absorption, no electronic transition, no color. There you have it!*

However, the MnO4^- ions are built different. Literally. The presence of oxygen atoms allows for a whole different type of electronic transitions - the so-called charge transfer transitions, where electrons are exchanged between the metal (manganese) and whatever's stuck to it (oxygen in our case). Obviously, these aren't d-d transitions. They aren't parity-forbidden. There's no stop sign here, the electrons can legally go wild. And they do - which is why the MnO4^- ions create such vividly colored compounds. Isn't that cool? :D

*"The probability that [an electronic transition will happen] reduces greatly" does not mean "This electronic transition will never ever happen." I told you, electrons are bastards. In fact, you can obtain an absorption spectrum of the Mn^(2+) ions and see some really nice peaks:

[via]

Clearly, light absorption does happen in the Mn^(2+) ion. But compare the intensity (y axis) of the peaks above with that of the spin-allowed transition in Cr^(2+):

[via]

We're talking two orders of magnitude of a difference here! Electronic transitions do happen in the Mn^(2+) ion. But so rarely it's as if they weren't there at all. CT transitions are very, very intense - again, orders of magnitude more intense. I like the Wikipedia page on CT bands, if you're really curious about this stuff.

You can read the rest of my sci comm-ish posts here!

[erbiumspectrum]

@studyblr-perhaps ah well you see, that's because in order to learn about all the fun things that physics causes you have to study chemistry. But in order to understand those fun chemistry things very deeply you have to study physics. You can't win, you can only suffer, but at least you get to choose the kind of suffering yourself (studying chemistry vs studying physics)

[studyblr-perhaps]

THIS IS SO TRUE SIGH

[orchidarcanum]

[magdalenism]

[ea-paperbits]

Women in STEM are just witches in white lab coats instead of black robes

art source: abigaillarson-Poisonous Plants irenhorrors-Drawlloween Laboratory

[erbiumspectrum]

Why some electronic transitions are forbidden and why that actually means jackshit

You'd be forgiven to ask, "Lena, what the fuck are you talking about" right away. "Forbidden transitions" sound odd if you don't know much about spectroscopy - but they're a very important concept. Still, electrons - the stars of electronic spectroscopy - are quantum bastards, and you can tell them something is "important" until your lungs give out, but they'll always do whatever the hell they want. And so is the case here.

Selection rules

Rules are meant to be broken. ---every electron ever, probably

In electronic spectroscopy we shine some light on matter and see what what happens to the electrons inside it. You may remember from your chemistry classes that atoms are built sort of like very complex onions: there are shells and subshells where all the electrons sit. Shining light on an atom may cause it to absorb some energy and go from its regular ground state to an excited state.

You may also remember your science teacher telling you that light absorption causes an electron inside an atom to "jump up to a higher energy level". It's bullshit, because electrons aren't fucking kangaroos and they can't jump. It'd be more precise to say that light absorption changes the quantum state of an electron, but a. hopping electrons are easier to imagine, and b. that just sounds like I'm evading giving you the full picture (which I am. Do you seriously want me to start yapping about atomic terms and angular momentum?).

But I digress. When an atom goes from its ground state to an excited state due to its electrons doing whatever the hell it is that they do when they absorb energy, that's an electronic transition. But just like traffic rules make some theoretically doable actions illegal, there are the so-called selection rules which allow for some electronic transitions and prohibit others.

The most important of them all states simply that energy can only be absorbed in discrete packets, and isn't very interesting. Another one says that the total spin of a system mustn't change during an electronic transition. Personally, I really like the Laporte selection rule (aka the parity rule). It forbids transitions between states of the same parity, like those between d orbitals.

But like I said, electrons are bastards. They break rules all the time. If they could drive a car, they'd go the wrong way up a one-way street and run over pedestrians with a gleeful screech. You can tell them what to do, but they'll just flip you off and fuck your mom. And you know what? It's fucking awesome that they're like that!

Screwing the Laporte rule gives us many pretty colors

A white powder always makes a chemist happy: you never know if it's sugar or amphetamine. ---a tour guide in my uni city's museum of pharmacy

But frankly, colorful crystals and solutions make us even happier. How boring chemistry - and the world, really - would be if electrons never violated the Laporte rule! I mean, just look at these:

[top left / top right / bottom pics are mine]

None of these compounds would be colored if it wasn't for electrons giving the finger to the Laporte rule. And the really cool thing is if you want to explain how this rule gets lifted, you have to turn to symmetry (when you really get to the bottom of things, there's always either QM or math there). The two major mechanisms that cause violations of the Laporte rule are orbital mixing and vibronic coupling (which is what happens when molecular vibrations team up with electronic transitions), both of which are very neatly dealt with by taking into account symmetry considerations. It's all very pleasing. Can you really judge me for having a favorite selection rule? Look how cool all this stuff is!

Screwing the spin selection rule gives us glowing things

I don't like luminescence thermometers. I miss being able to just buy a mercury thermometer wherever. ---my fundamentals of chemistry lecturer, who researches luminescence thermometry

Like I've said many times before, an electron is not a marble: it isn't actually spinning or orbiting the nucleus. Still, there are two important vectors associated with it, representing the orbital angular momentum and spin angular momentum (yet another proof that electrons are bastards). When these two interact, they can give rise to the so-called spin-orbit coupling which, in turn, is able to change the total spin of the system.

But violating the spin selection rule is sort of harder for electrons to do, so it takes them a long time to emit all the extra energy and return to the ground state. We call this relatively slow process phosphorescence. Your childhood glow-in-the-dark star stickers? Some exit signs in public spaces? That's spin-orbit coupling and electrons being rebellious baby!

What's not to love. Spectroscopy is so fucking awesome <3

You can read the rest of my sci comm-ish posts here!

[frenchiepal]

01.06.26 🍀 not doing super well. there's so much to do and so many deadlines, everything stresses me out. the only ray of hope is that the worst will be over by next week, and that i got to attend a frog party 🐸

[erbiumspectrum]

This used to be a thing a while ago and I really wanted to bring it back, so here's ✨a bingo tag game for ya✨

Rules: mark all that apply to you and see if you get a bingo :D Then make a bingo card of your own (I used this website) and tag whoever you want to join the game!

@ceciliasinmapockett @lost-rxverie @studyblrspace @stargazerbibi @hydroflouricacid @studiousandrogynousfox-blog @winryrockbellwannabe @getbreaded @cyberstudious if you guys wanna play with me 👉👈

[studyblrspace]

bingo :D

[hydroflouricacid]

Thank you for the tag! Bingo :3