[Jimbee (OP)]

I've always wondered. What color are atoms? And do they even have a color? And what shape are they? They're always depicted as spherical. That makes sense. Planets are spherical, raindrops are spherical. It's the default shape to take when nothing forces you into another shape. But are they?

[Kryptid]

Individual atoms are smaller than the wavelength of visible light, so I don't think they have a color (someone more knowledgeable feel free to chime in on this if I'm wrong).

The shape of atoms varies from one to the other, but they tend to be roughly spherical. It's determined by the shape of the orbitals that electrons occupy: https://en.wikipedia.org/wiki/Atomic_orbital

[Bored chemist]

We don't usually encounter individual atoms because they stick together and form molecules.
Some gases consist of individual atoms.
One such is sodium vapour and it's noted for very strongly absorbing visible light but only at a very limited range of wavelengths.

There might  be circumstances where sodium vapour would look blue, especially at high temperatures and pressures.

Not an experiment I plan to do soon...

[paul cotter]

How about an atom of bromine, BC. Being a strongly coloured substance that does not rely on any structure in the massive state to account for it's colour. On second thoughts the colour may be a function of the bromine molecule rather than the atom.   

[Bored chemist]

On second thoughts the colour may be a function of the bromine molecule rather than the atom.   

It is.

Bromine atoms may well be coloured, but you seldom encounter them.

[alancalverd]

Anyone who has seen DNA knows that carbon atoms are black, hydrogen white, nitrogen green and oxygen blue. In the brave new world. models are more important than reality.

[paul cotter]

I have done a lot of catalytic hydrogenations and the hydrogen is always colourless and then I hear talk of green hydrogen, brown hydrogen and grey hydrogen. They must be dyeing the gas, yes??

[alancalverd]

It's a potentially serious problem! I've been advocating a change from methane to "green" hydrogen as the principal domestic and industrial energy source because it solves a lot of problems at negligible cost. It's also the ideal fuel for transport, but I think there's a snag.

Mains gas always has a trace of mercaptan or hydrogen sulfide to warn humans of leaks and unlit burners. It would be enormously advantageous to use the same distribution system to power electric vehicles but sulfur compounds can poison fuel cells. So here's a question for my friend and nemesis BC: is there any other volatile stinky tracer that can be added to hydrogn and not subtract from fuel cell efficiency? Or any simple means of scrubbing mercaptan from mains gas?

[Bored chemist]

The problem is known and being worked on.
As a pilot, it's easy enough to put in charcoal filters to scrub out mercaptans for hydrogen used in fuel cells..
In the longer term there are proposals for using other stenching agents.
Another point is that it may be useful if "hydrogen smells different from gas".

https://www.sciencedirect.com/science/article/abs/pii/S0360319920306595

If we were able to magically stop using gas in pipes today and use H2 instead, my guess is that it would be 10 years or so before the network stopped stinking of mercaptans.
So, any "H2 for fuel cells" would still need a separate distribution system or a scrubber.
Fortunately, charcoal works pretty well.
Regenerating it would be interesting.

[paul cotter]

Interesting link, BC, thank you. I was disappointed that the "table #1" of odourants was not shown without downloading the full article which I can't do without buying it. I presume tht refers to tetrahydrothiophene. Isobutyl isonitrile has a dreadful odour, like all isonitriles, but I doubt if it would be stable long term. Hydrogen selenide is another horror that might be a catalyst poison also. In fact all the nasties I can think of are all of dubious stability or catalytic poisons.

[Bored chemist]

There is an underlying issue.
In general, things that stink are bad for you; that's why you think they smell bad. It's meant to be a warning.

[alancalverd]

The non-chemist solution would be to run the high pressure (150 bar) crosscountry grid lines on pure hydrogen with maybe a charcoal scrubber to clean up the legacy residue at the vehicle pumps (which appreciate a high input pressure)  and add the stink at the point where the grid drops down to domestic/industrial burner pressure.

Where you have a small number of high-density pipes in open spaces (garages, railway sidings, etc) you can detect pure hydrogen leaks with simple electronics - less sophisticated but more precise than a human nose.   

Selenide? Ye gods! If you think H2S is bad.....

[Bored chemist]

The non-chemist solution would be to run the high pressure (150 bar) crosscountry grid lines on pure hydrogen with maybe a charcoal scrubber to clean up the legacy residue at the vehicle pumps (which appreciate a high input pressure)  and add the stink at the point where the grid drops down to domestic/industrial burner pressure.

Congratulations on predicting the system that is already in place.

" Modern day natural gas in the United Kingdom is odourised in only the lower pressure distribution pipelines using an odour blend referred to as NB"

From
https://www.sciencedirect.com/science/article/pii/S175058361500153X

[alancalverd]

So: full hydrogen ahead!

[Bored chemist]

So: full hydrogen ahead!

...as long a the only problem is what it smells like...

[paul cotter]

Diffusion and embrittlement. An off topic question: does the smell of the group 6 element hydrides continue to worsen with increasing atomic weight, ie would hydrogen telluride smell worse than the selenide? I doubt it would be stable for long at stp.

[alancalverd]

So: full hydrogen ahead!

...as long a the only problem is what it smells like...

Frankly, yes. The industrial world ran on 50% hydrogen for around 100 years with fewer problems of embrittlement than Windscale and fewer long-term disasters than Chernobyl, so it seems like a good idea to supplement a safe power source with an even safer one!

[Bored chemist]

The industrial world ran on 50% hydrogen for around 100 years

And this happened .

co2 graph.png (28.35 kB . 434x372 - viewed 592 times)

[alancalverd]

Yes indeed. According to that graph, atmospheric CO2 began to increase as soon as coal gas was replaced by methane.

[Bored chemist]

Yes indeed. According to that graph, atmospheric CO2 began to increase as soon as coal gas was replaced by methane.

No. It was rising before that.
". 1965 North sea gas discovered in the West Sole field. 1968 Natural gas conversion programme starts at Burton on Trent. 1976 Natural gas conversion programme completed."
From
https://www.nationalgasmuseum.org.uk/discover/

Perhaps it's unwise to post a little after 4 in the morning.