How To Understand Resonance Structures using Cute Balls

There comes a time in every man’s (or woman’s/other’s/etc) life that they have to learn about resonance structures and delocalized electrons. Or probably not. I don’t think most people know what it is. But you’re going to! Right now. No, you don’t have a choice in the matter. You clicked on the link, you knew what you were getting into. 

• Resonance Structure
• Carbocations
• Aromatics

Electron Quantum Bullshit

This next part I’m going to say is a massive oversimplification for the purposes of teaching chemistry to the uninitiated. If this was a physics article I’d explain it very differently, so don’t quote me.

It is important to accept that electrons aren’t really “tangible”. They certainly aren’t little copper colored balls flying around some raspberry looking nucleus.

Unlike the atom as a whole, electrons obey quantum physics and so play by entirely different rules. If you already have an understanding of what a lepton is, go with that. 

Every electron, when unobserved, exists everywhere in the universe simultaneously. But it’s *mostly* only able to physically interact with a relatively small area of space, namely an area around its atom called its “orbital”. 

Again, the electron doesn’t actually orbit. If something tries to interact with or observe that electron and the waveform collapses, there’s a very high probability it will be in that area. 

If you’re a bit confused by that (which is fair as this is literally beyond human comprehension), it’s helpful if you don’t think of an electron as an object. Think of it as more of a “field”, or an “essence”, or some shit like that. Any given electron “field” has much more influence in the area around the nucleus than it does anywhere else. The further away from the nucleus, the weaker the electron gets until it’s basically undetectable.

Electronball Delocalization and Resonance Structures.

A lot of molecules, especially organic molecules, have what are called “resonance structures”. ¹I have a physics major friend, and she strongly dislikes the term “resonance structures”. Since that’s not what resonance is. Which is why I exclusively call it that. Also because it’s by far the most common search term and I need to optimize for search engines.

Because electrons kind of exist everywhere, there isn’t really anything other than random probability keeping them attached to a single atom. So sometimes, atoms bonded to each other can exchange electrons between them.

Let’s use the sulfate ion as an example, which is what sulfuric acid looks like after it’s kicked out it’s hydrogenballs. You may wonder how a sulfate ion could be a stable molecule at all, it has two negatively charged oxygens! Oxygen is an extremely clingy element that really doesn’t like being not bonded to stuff. 

Well, turns out the sulfate ion is relatively stable because of its resonance structures. Chemical bonds are made out of electrons. So sulfate can take those electrons out of its double bonds to fill the gap in oxygen’s valence shell. 

But it can also move those spare electrons floating around the Oxygenball and put them back into the oxygen-sulfur bonds, stabilizing the molecule.  

When this was first discovered, chemists thought that molecules were just switching between the different configurations really fast. Hence why they called it resonance. But, of course, that would be too easy to understand so it can’t be right.

In reality, a molecule’s properties are the weighted average of the properties of all its resonance structures. And I don’t mean that the properties of a test tube of sulfuric acid is the weighted average. I really do mean each individual sulfate molecule exists in a state that is intermediate between the theoretical states of its resonance structures. 

Let me make sure I’m being clear, as I’ve had people read this and think I meant it metaphorically or something. This isn’t metaphorical. 

Each individual oxygen around the sulfur does not have a 50/50 chance of having either -1 charge or a neutral charge. Each individual oxygen has a charge closer to -0.5 as one of the electron “fields” is being split between it and the bond.

Imagine that I exist in a similarly delocalized state between baking a cake, answering a text, and slapping you on the face. I’m a zoomer and am therefore able to multitask, but not very well. 

So I only make a third of a cake, only spell every third word on the text correctly, and just lightly tap you on the cheek. Also I exist in three different places simultaneously, but each copy of me is transparent and only weighs a third of my normal weight.

Just to check that you’re following me. Remember that this involves quantum physics voodoo. So if whatever you are imagining is happening here makes sense; you have it wrong. This isn’t easy to understand because the human brain was not made to comprehend it. 

The normal convention when talking about this or drawing diagrams is to act like molecules do switch between configurations really quickly because that’s easy to understand, but it is also not a true representation of what is happening.

Sulfate with -1 charge oxygens would be unstable. But -0.5 charge oxygen is stable enough. In fact, when it’s also surrounded by water molecules that can neutralize this charge, sulfate is even more stable than sulfuric acid with the hydrogens attached. 

This is what makes it such a strong acid. Sulfuric acidball feels it would be better off without the hydrogen so it kicks them out as soon as it’s possible. Then the hydrogen goes and attaches onto some unlucky molecule, damaging it in the process. 

Carbocations and their Resonance Structures

Standard practice in chemistry is to call a positive ion a “cation”²pronounced: “cat-ion”. I once had a classmate who pronounced it “kay-shun”, then everyone laughed at him. I was pretty funny, to be honest. My friend from earlier uses the mnemonic “cats are always positive” to remember that cations are the positive ions. Chemists also like to call carbon cations “carbocations”, I guess because that one extra letter was way too difficult to say, because as we all know chemists hate word salad terminology /s. And standard practice on r/chemiballs is to draw cationballs as cute neko cats.

As you would know if you read my previous article on Carbonball, Carbonball doesn’t fucking like being ionized. This is because Carbonball ain’t a furry and doesn’t like wearing cat ears and a tail plug. For a long time chemists didn’t think it was even possible for carbons to be ionized because they’re just too unstable.

It turns out it is possible to have a relatively stable Carbocationball, so he’ll try to push the positive charge down the chain. 

For example, here is the molecule pentadienyl cation. The five carbonballs in it don’t have enough electrons to go around. So they share the shame of the cat ears between them using quantum physics voodoo known as electron delocalization. That way, instead of one carbon being 100% a furry, each is just 20% furry.

Remember, this isn’t like one electron is moving between the carbons really fast. One electron is being split between multiple carbons simultaneously, which is more stable than if just one having a charge of +1. The molecule as a whole has a total charge of +1.

Aromatics

This whole thing can also apply to bonds. Most of the strength of materials comes from how good their bonds are. A carbon=carbon double bond is much stronger than a carbon-carbon single bond. Likewise, a carbon≡carbon triple bond is even stronger. 

But just because you have a material with lots of triple and double bonds doesn’t mean it will be strong if it still has some single bonds, because a chain is only as good as its weakest link. So the best way to have an organic molecule that is really strong and stable is to make sure it doesn’t have any carbon-carbon single bonds. 

As you’ve seen in our prior examples, electron delocalization doesn’t just affect the charge of atoms but also their bonds. When you have a bond that is a single bond in one resonance structure and a double bond in another, it’s not actually going to be a single or double bond. It is, in fact, a one-and-a-half bond and its strength is between that of a single and double bond.

Aromatic molecules have a configuration that allows for some really fancy electron delocalization giving them this heightened state of stability. They also have some other neat features I’m not getting into right now. This makes them super chemically stable, and hence appear frequently throughout chemistry.

They are called “aromatic” because in the past, chemists thought that certain smells only came from aromatics. This turned out to not be the case. But chemists still call it that because they’re too lazy to rename anything. 

The simplest, most famous, and most important aromatic molecule is benzene, which is illustrated above. In fact, Benzeneball and it’s derivatives appear so frequently that a common joke about organic chemistry class is that the only skill most people learn from it is drawing hexagons. Benzene also happens to be my favorite molecule. And yes, I do realize having a favorite molecule is an incredibly normal and admirable thing to do.

Addendum

For more Chemiball stuff, check out r/Chemiballs. This is a shockingly obscure community and deserves more attention.

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