1. Helium has a near identical melting and boiling point, and the lowest of all the elements. It’s melting point is so close to absolute zero that nothing else is cold enough to freeze it, so scientists have to use specially built pressure chambers to solidify it.
2. It is stable with just two valence electrons as opposed to all other noble gases requiring eight electrons.
3. Near absolute zero, helium becomes a superfluid where it gains zero viscosity.
4. It has the highest thermal conductivity of any element which makes it an excellent coolant.
5. It is naturally non-toxic and the most chemically inert of all elements.
6. One of it’s only known ions, helium hydride, is the strongest acid ever observed.
What gives? Why is it such a wonder substance and why does it display such unique traits compared to other elements?
In: Chemistry
There are a couple reasons, depending on which question you’re asking. I’ll start with the easy ones.
2, 5, and 6 are all because that’s how the electron shells of atoms work. Helium has 2 protons, so it can only have 2 electrons (or else it would be an ion). As such it fills the 1s orbital, the lowest energy orbital, and the highest energy orbital when all lower orbitals are filled. It and hydrogen are the only elements that have the 1s orbital as the valence shell because all others have more than 2 electrons when electrically neutral. Additionally because it is electrically neutral when shells are filled, that means that it will resist reacting with anything. All noble gases are like this, but because helium is so small, it has a tighter grip on the outermost electrons than others so it’s even less reactive. If you manage to get it to react with something there is a lot of energy in there, and so you can make some crazy reactive things.
4 is wrong. Helium is a very bad conductor. Silver is the most conductive element iirc, because it is a metal with the right number of valence electrons and size to just be super conductive.
And finally the rest. Helium is made of 2 protons, 2 neutrons, and 2 electrons. That is an incredibly stable combination. All three of these things have spin. Think of a yin yang symbol, each of the energy states of everything with spin half (fermions) is one half of that, and when you get two they can fill that energy state and become super strong and stable. They lock into place. This is what’s happening below the valence shells in atoms btw and helps explain the parts I explained above as well. As a result of this, helium really doesn’t care about interacting with anything, including itself. So when you cool it, it doesn’t care that it’s getting closer to others of the same type it just happily goes floating along still. And that’s what a gas is: a type of particle that is moving fast enough that it avoids interacting with other particles of the same type, so it can’t stop moving like it is. Some things really don’t care much, like hydrogen atoms, so you need to get them pretty cold to interact like a liquid. And very very cold to interact like a solid. But hydrogen still cares a little. Helium though? Helium is head empty only move. It needs to be cooled so much that quantum effects manifest on non quantum scales before it cares what other helium atoms are doing. At that point we need to care about that spin again. Spin half particles cannot occupy the same energy state. Whole integer spin particles, bosons, can. Helium is made of 2 spin half protons and 2 spin half neutrons. This cancels out to make it spin 0 overall. When cooled enough it begins to act like a boson, a bose-einstein condensate actually, and all those normally distinct helium atoms begin to be…the same. Kind of. So when you move one of them, they all move together. They can no longer give up any energy, so can’t stop moving from friction: zero viscosity.
The important thing here is the spin. Everything has energy states, and the three fermions we care about here have spin 1/2. This means helium, with its 2/2/2 makeup, is at the lowest energy possible while having the highest and lowest shells filled for all of them. This combined with its size explains all of this.
This was a mess but hopefully it helped a little?
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