Metals are characterized by free movement of electrons throughout the substance. That is why metals conduct. Hydrogen is also in group 1 of the periodic table due to a single unpaired electron but on Earth, shares little with the other metals in that column such as sodium.
Hydrogen is also in group 1 of the periodic table due to a single unpaired electron but on Earth, shares little with the other metals in that column such as sodium.
Under 2 million atmospheres of pressure, a mass of hydrogen will become degenerate matter, packing in electrons so tight that violation of the Pauli exclusion principle starts coming into play. As more mass is added and pressure increases, the electrons are forced to move further and further out in velocity space to avoid overlapping in physical space.
The result is a cloud of electron "gas" moving freely through a solid crystal matrix of hydrogen nuclei (bare protons, really). That's exactly the same structure as any other metal, and matches what we've created in the lab with diamond anvil experiments - under extreme pressures, we see hydrogen transition to a grey and lustrous material that's a good conductor of heat and electricity.
As I said...on Earth it shares little with anything else. And so far as I know, has not been generated, and is all based on theory. I mean, I have a doctorate in analytical chemistry, so my inorganic and physical chemistry knowledge is not extremely deep. But the few very general statements have I made are correct so far as I know.
Metals characterized by non localized electrons.
Hydrogen is in group 1.
Has a single unpaired electron.
Shares little with other group 1 metals.
I took it as understood that if metallic hydrogen has non-localized electrons, then you have a bunch of bare protons. That is why it behaves in ways similar to a metal.
Cool, I have a doctorate in astrophysics, specializing in giant planet atmospheres. We are very, very closely watching the lab work on metallic hydrogen come out, as we're fairly sure literally no other substance can fit all the Jupiter observations, notably density and magnetic field shape. For example, Jupiter's strong quadrapole moment and toroidal component of its magnetic field help us constrain the upper and lower depth of the dynamo annulus. Probably more than a coincidence it seems to starts somewhere around the million-atmosphere level, extending down to the edge of the rocky core. All our equations-of-state tell us hydrogen should be a liquid metal in that range.
And so far as I know, has not been generated, and is all based on theory.
Researchers have been making metallic hydrogen in the lab for over 20 years now, usually creating it for a split-second with some kind of shocked implosion, though diamond anvils are now approaching the necessary pressure range. Citations start with Weir, et al (1996), conductivities were measured by Ternovoi, et al (1999), deuterium was made metallic by Celliers, et al (2000), claims of atomic metallic hydrogen were made by Badiei, Holmlid (2004), and so on.
on Earth it shares little with anything else.
Sure, lots of substances are like that at high-pressure. Water at STP is a liquid; keep it room temperature but increase the pressure to 10,000 bar and it becomes an ice. Keep adding pressure and you get superionic water, a metalloid slush. Keep going and eventually it dissociates, oxygen becomes a red crystal, until eventually it too turns metallic.
Shares little with other group 1 metals.
Right, I think this is our point of contention, and probably due to the difference in our fields: chemistry defines metals as specific groups on the periodic table. Physics defines metals as solid / liquid materials with an imaginary index of refraction and a negative permittivity, usually due to an electron gas, though other diffuse ions can work (e.g. superionic water as the dynamo source for Uranus and Neptune).
To be clear, I'm in no way saying that high-pressure hydrogen is a metal because it's in the same group with the alkalis. Again, at even higher pressures, oxygen becomes a metal...and eventually so would every other element as it goes electron-degenerate. At that point the only phases available are either metallic (cold enough that the crystal hasn't vaporized) or plasma (hot enough that it has).
it behaves in ways similar to a metal.
Yeah, I guess that's my point. From a physics standpoint, metallic hydrogen is not similar to a metal, it is a metal by any measure. Just because it doesn't behave like a metal at STP doesn't make it any less of a "true metal" at high pressure.
"Metals are characterized by free movement of electrons throughout the substance. That is why metals conduct. Hydrogen is also in group 1 of the periodic table due to a single unpaired electron but on Earth, shares little with the other metals in that column such as sodium."
Can you please explain what about this is a problem exactly? Also, I am not disputing the existence of metallic hydrogen, I just said it hadn't been observed to my knowledge, which I admit, is limited in the realm of physics, and certainly astrophysics. I also would be very surprised to find things like superionic water and red crystal oxygen occurring on Earth, outside of a lab, and for brief moments.
I have no idea what got panties in a wad about my original post, or second for that matter but its all literally first semester gen chem. So I guess kudos, you have informed me that we can make it for brief instants in a lab. Now I remember why a post I saw on the front page makes sense.
"Don't waste time arguing with strangers on Reddit."
I didn't think we were arguing, just having a discussion on the use of "metal" as scientific terminology. I'm not sure exactly what you took offense at, but it wasn't my intention.
I have no idea what got panties in a wad about my original post, or second for that matter but its all literally first semester gen chem.
The original post asked about metallic hydrogen on Jupiter. You corrected them by pointing out hydrogen is generally not a metal on Earth. While true, that's not super-relevant to "on Jupiter", where most of the hydrogen by mass is in a metallic state. Since you seemed to be unaware of this context, I tried to educate you. Again, I'm not sure what's offensive about that.
Now I remember why a post I saw on the front page makes sense.
"Don't waste time arguing with strangers on Reddit."
Also not quite sure what you saw as grounds to break civility here.
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u/SonumSaga Dec 29 '20
That's why it's a gas giant :D