The colour of Hydrogen

What colour is liquid hydrogen?

All references to the element, I can see, say it is a colourless gas, but what is it like when it is a liquid?

Is it ‘clear’ as in actually colourless or just appears nearly colourless.

Eg. Water is light blue, as is liquid oxygen, as is hydrogen peroxide etc.

Hydrogen is a metal, so I’d assume it would look somewhat… metallic?

I’m reasonably certain that Hydrogen is colorless. Oxygen is blue because of electronic transitions in the visible range. Hydrogen will have no electronic transitions in this range. Water is blue due to the fourth harmonic of the O-H stretch in the infrared. Hydrogen will not be infrared active. I can think of no transitions in the visible range for hydrogen.

Hydrogen is a metal? Not by any standard definition. It is about as far from metallic as you can get.

Hydrogen can be metallic, under the appropriate circumstances of temperature and pressure. But if you simply cool it down under atmospheric pressure, it’s a liquid. I think it appears slightly bluish, but like most liquified gases, it’s pretty clear and not obviously colored.

Hydrogen is placed on the periodic table as an alkali metal. While it is not considered to be a metal under normal conditions, at high enough pressures it is theorized that it will take on metallic properties.

From here: Metallic hydrogen - Wikipedia

I’ve heard liquid hydrogen described as colorless. I’ve also heard it described as being pale blue, which makes me think it looks a lot like water. I personally don’t just happen to keep a bucket of the stuff handy in case this question comes up though.

I’m well aware of metallic hydrogen. If you compress helium enough then helium will also be metallic. Are you going to claim that helium is a metal too? In fact, I’ll bet if you compress any element to the point that the electron electron repulsion raises the ground state into a conduction band you’ll get the same thing. By calling hydrogen a metal, you are essentially saying that all elements are metals.

Hydrogen is not classified as an alkali metal. It is classified on it’s own because it can react in ways that alkali metals cannot react. Any classification scheme that puts hydrogen in the alkali metal category is completely ignoring it’s covalent and hydridic reactivity. That’s not useful.

The wiki page on Liquid hydrogen lists its appearance as “colorless liquid”.

So… if the gas giants in our solar system were pure hydrogen without anything else, they’d be white?

Cite? I’ve never heard of metallic helium before.

Here is a cite. I’m sure as a physicist, you are better equipped to find better cites.

I’m not a physicist, but it makes sense to me that this should eventually happen to any element with enough pressure. I think of the electronic energy surface as a series of hills and valleys. In non metallic elements, the electrons are localized in the valleys, but as you compress them the valleys will rise in energy due to electron electron repulsion. Eventually, I think that the difference between the energy of the hills and the valleys will be small enough that the valence electrons will no longer be localized.

Of course the hills will rise to, and this assumes that the hills won’t rise as fast as the valleys. Also, I have no idea if the amount of pressure required to get to this state will be enough to breakdown other barriers like nuclear.

Are you claiming that hydrogen is never ever classified as an alkali metal, anywhere, by anyone, under any circumstances?

From: Corrosion Source

I have seen liquid hydrogen, but frankly there was so much condensation in the air that I can’t say what color the liquid is. Very little if any color though.
I can say by direct observation that liquid helium is a clear liquid. No trace of color that I could see. And we were lighting the liquid to observe superfluid behavior.

Hydrogen is often categorized as an alkali metal by elementary school teachers, non-chemists and OCD people that look at it’s place in the periodic table and stick their fingers in their ears when you mention hydride just so they can make it fit.

Hydrogen is in every respect a unique element and nobody with any sense would classify it as an alkali metal. Hydrogen is not a metal.

Is water really blue?

I was taught in school that the ocean appeared blue because it was reflecting the blue of the sky. Although now that I think about it, the sky is a much lighter blue than the ocean.

Have you ever seen an indoor pool?

I’ve never seen one that did not color the sides of the pool blue, and the water has never seemed any bluer than the sides.

I also thought it was due to coloring the surface. I have seen some outdoor pools where the water is green. Not due to algae but because the pool surface is green.

They tried to teach me that too, but I never believed them. I find the persistence of this myth quite remarkable, as the sky is blue for probably less than half the time here in England - so we have abundant opportunity to observe the falsity of the claim.