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
1. I don’t know for sure about this one, but I would bet that it’s because it’s the smallest noble gas. Interactions between atoms increase in strength with size, and helium is already non-reactive because it’s a noble gas, so together, that makes it really easy for helium atoms to split apart into a gas.
2. It’s stable at 2 valance electrons because there are only 2 possible ground states electrons can be in with 0 angular momentum. Once those two fill up, any further electrons added to an atom need to have higher energy, and there are a lot more available states with nonzero angular momentum (meaning a lot more electrons needed to fill them up and become stable)
3. Helium becoming a superfluid is related to it having 2 neutrons and 2 protons. Each of those has 1/2 spin, so adding them up makes helium have an integer spin. Particles with integer spins are called bosons, and can form a state known as a Bose-Einstein condensate where all particles are in the same quantum state. This Bose-Einstein condensation is what leads to superfluidity.
4. Thermal conductivity is heavily dependent on state, so this definitely isn’t always true.
5. Non-toxicity is more to do with human evolution than helium itself, though not being reactive probably helps with that. It being non-reactive is again due to the fact that it’s a neutral particle that has a completely full ground electron state, so gaining any electrons takes a lot of energy, and losing any takes a decent amount too.
6. Acidity is related to how easily particles release hydrogen ions into solution. Helium hydride is basically just regular helium with a single hydrogen ion hanging out nearby. The single hydrogen ion hanging out nearby means that when you stick it into water, it’ll *very quickly* ditch the hydrogen ion and just go back to being helium, which is why it’s a strong acid.
Most of these are results of helium being the smallest stable atom to completely fill its electron states, and helium being a boson.
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