John Carlos BaezJun 9, 2024

If you could watch an individual water molecule, about once in 10 hours you'd see it do this!

As it bounces around, every so often it hits another water molecule hard enough enough for one to steal a hydrogen nucleus - that is, a proton - from the other!

The water molecule with the missing proton is called a hydroxide ion, OH⁻. The one with an extra proton is called a hydronium ion, H₃O⁺.

This process is called the 'autoionization' of water. Thanks to this, roughly one in ten million molecules in a glass of water are actually OH⁻ or H₃O⁺, not the H₂O you expect.

And this gives a cool way for protons to move through water. Let's watch it!

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Show threadL

@johncarlosbaez that was quite unexpected. From my middle school education I convinced myself that only electrons can jump from one atom/molecule to another, not nuclear particles.
And positive ions, are just atom that lost some electrons (but same atomic number).

So this story makes me have some sci-fi thoughts. I'm a bit naive but... that's what I'd ask writing a sci-fi book on it.

1. Does this enables, somehow, "protonic" current flowing into suitable "water circuits"? Or the structures arising always prevent this current from happening?

2. I believed that the electric charge of 1 electron balances perfectly the charge of 1 proton, as 1+(-1)=0. So why the hydronium ion missing only 1 electron to be "neutral" attracts so many water molecules?

3. Such structures that are then formed in water... are they visible? Ideally how large they can get? I wonder if they get large enough they makes water in a state that is neither liquid or solid.

Jun 9, 2024 at 4:54pmWeb
Show threadJohn Carlos BaezJun 9, 2024

Nice questions, @leemph!

1. " Does this enables, somehow, "protonic" current flowing into suitable "water circuits"?"

Inside the Grotthuss mechanism I discussed, shown below, seems to be one of two important mechanisms for protons to move through water, the other being 'vehicular transport' where they move as part of hydronium ions H₃O⁺:

https://www.sciencedirect.com/topics/engineering/grotthuss-mechanism

2) "I believed that the electric charge of 1 electron balances perfectly the charge of 1 proton, as 1+(-1)=0."

That's true.

"So why the hydronium ion missing only 1 electron to be "neutral" attracts so many water molecules?"

In the van der Waals effect, a positively charged particle can polarize nearby neutral molecules, pulling their negatively charged bits towards it and repelling their positively charged bits. Then these neutral molecules are attracted to it!

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Show threadJohn Carlos BaezJun 9, 2024

@leemph -

3. "Such structures that are then formed in water... are they visible? Ideally how large they can get?"

I don't think they get so large as to be visible, but they get quite large! Here is a hypothesized "icosahedral water cluster". In reality they aren't so perfect, since they're always being buffeted around by other water molecules.

For more see this:

https://water.lsbu.ac.uk/water/icosahedra.html

Icosahedral water cluster symmetry and architecture