
Relativity behind mercury's liquidity (2013) - zeristor
https://www.chemistryworld.com/news/relativity-behind-mercurys-liquidity/6297.article
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zeristor
It seems this Wikipedia article on why Gold is yellow was posted a while back:

[https://en.wikipedia.org/wiki/Relativistic_quantum_chemistry](https://en.wikipedia.org/wiki/Relativistic_quantum_chemistry)

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peter_d_sherman
>"In the 1960s, Pekka Pyykkö, now at University of Helsinki, Finland,
discovered that gold’s colour was the result of relativistic effects. He
showed that the lower energy levels of the 6s orbital of gold means that the
energy required to excite an electron from the 5d band lies in the visible
rather than UV range of light.

This means that gold _absorbs blue light_ , while reflecting yellow and red
light, and it is this that gives the metal its characteristic hue."

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zeristor
So are even heavier elements more interesting. I would expect more coloured
elements, more liquid elements at room temperature for heavier elements.

Can the number of neutrons in an isotope make a big difference, there are a
few elements which have a wide range of isotopic weights, if a property was
quite delicate I’d expect such changes to be quite apparent, tricky for
millisecond half lives.

~~~
FreeFull
One thing that comes to mind is
[https://en.wikipedia.org/wiki/Kinetic_isotope_effect](https://en.wikipedia.org/wiki/Kinetic_isotope_effect)
, although this seems to mostly affect elements that only have a few protons,
like hydrogen or oxygen. Still, it adds up enough so that replacing most of
the water in your body with heavy water (D₂O) would be fatal.. But, you'd have
to drink exclusively heavy water for a long time to actually reach a toxic
dose.

~~~
zeristor
Yes thanks for reminding me about Heavy Water ice, and how it sinks in a glass
of water too.

Also I have subscript envy, and shall scour the Internet as to how to do
subscripts in HN.

~~~
FreeFull
I used the subscript 2 unicode character (U+2082). As far as I know, HN's
formatting doesn't include anything to do subscripts. (At least,
[https://news.ycombinator.com/formatdoc](https://news.ycombinator.com/formatdoc)
does not mention it.)

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throwaway_pdp09
I understand electrons are a probability cloud but suddenly

> The larger the nucleus gets the greater the electrostatic attraction and the
> faster the electrons have to move to avoid falling into it

and now they're moving (and in this case, faster). So how does a particle with
no attributable position move faster? This doesn't make sense.

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MockObject
It's a probability cloud of different possible locations, but also it's a
probability distribution of different permitted possible speeds, as well. This
probability distribution has a peak (a mode). When he writes "the faster the
electrons have to move", he means this mode for a heavier nucleus is larger
than that of a lighter nucleus.

Please let me know if I'm not being clear enough.

~~~
throwaway_pdp09
Actually thanks, that's very clear at that level, however that leads to a
further confusion (of mine) about what _speed_ implies, that being that the
electron is moving (obviously) from x to y, which apparently contradicts the
_probability cloud_ concept of probabilities of a position at instant x, and
only for that instant.

That is, if it's moving from x to y (because it has speed) then it's more
likely to appear on some vector between x and y.

Please feel free not to answer that question, as I may drag you down the
rabbit hole - but if you can, I'd love to know.

~~~
yomly
If you have a probability distribution of position.

Then increment time by one tick. If you have a second probability distribution
(assuming some time dependence) then you have now a distribution of distance
travelled and therefore a distribution of speeds.

The alarming thing about QM is that it is fundamentally probabilistic and yet
a little classical at the same time.

~~~
AnimalMuppet
I don't think that's right. If you increment the time by one tick, you have
the _same_ position probability distribution. That is, the wave function
didn't change. Why should it?

But that position probability distribution has a very specific energy. And at
each point of that position distribution, the electron has a specific
electrical potential energy. So at each point, it also has to have a kinetic
energy. It has a kinetic energy probability distribution to match the position
probability distribution. And now we can talk about velocity.

