Helium (He): My Favourite Chemical ElementPositronWildhawk There's antimony, arsenic, aluminium, selenium, but of the many elements, the greatest one is helium.
Helium is a chemical with so many unique and fascinating physical properties, and has heralded many an important scientific discovery. Whether observed as yellow and blue Fraunhofer Lines in stars, or obtained from the 5.2 parts per million in our atmosphere, Helium has done a lot for us. I can't speak highly enough of it. But without necessarily inhaling it, I'll stress my toast to this gas, gas, gas as much as I can.
What is helium, some of you may be asking? It is the second element on the Periodic Table, and the first noble gas.
Its atoms consist of a nucleus with two protons, and most commonly one or two neutrons, the latter being most abundant. Helium has nine isotopes, but only those two are stable, and a He-2 nucleus (diproton) is, in fact, the most unstable isotope known to man, and only exists for insignificant times in rare diproton decays and light hydrogen fusion.
Helium's atoms are, with the exception of synthetic muonic hydrogen, the smallest in atomic radius of all, at 31 picometers. Being one of two elements with one electronic shell, its only competition is with hydrogen. Sure, the two electrons in helium repel each other, but they're each attracted to a doubly charged nucleus. This is essentially a quantum mechanical three-body problem, and it computes that each electron experiences a net force in towards the nucleus of 1.7 times the force of attraction in a hydrogen atom. And as the two electrons fill the K-shell, this makes helium chemically inert and monatomic, which defines it as a noble gas.
The discovery of helium was a big step for solar physicists and astronomers. These scientists had been identifying the chemicals within stellar objects by means of lines in emission spectra. Each atom has its distinctive configuration of electrons, which produce a specific spectrum when the electrons are excited and subsequently de-excite. The electrons can only occupy discrete energy levels, and so when they de-excite, they emit the energy difference between its state and the ground state in the form of a photon of light, whose energy is proportional to its frequency. Thus, the emission spectrum of an excited substance is an indicator to its chemical composition.
It was the French astronomer Jules Jannsen who discovered a unique, unrecognised spectrum when diffracting solar light during an eclipse. The spectrum showed some mysterious bands of yellow light, whose frequencies were not yet documented together in spectroscopy. It was deduced that this was an undiscovered element, and it was named Helium, after Helios, the Greek God of the Sun. Thus, helium was the first element, and chemical, not to be discovered on Earth, and in the form of an ionised plasma. It was also this discovery which forced chemists to dramatically refine the periodic table, then based on the heavily flawed law of octaves. Helium was later rediscovered on Earth in the spectrum of lava at Mount Vesuvius.
Helium's later applications in nuclear physics were yet more significant in the name of science. From the study of radioactive decay, Rutherford classed the radiation emitted from unstable nuclei according to their magnetic and penetrative properties, one of these classes being alpha decay. Alpha rays appeared to consist of heavy, positively charged particles, with high ionisation and low penetration ability, and Rutherford hypothesised that they were identical to helium nuclei. He later confirmed that this was the case when he allowed alpha particles to enter a vacuum chamber, and then injected an electronic spark, which produced the Fraunhofer line spectrum associated with helium. The prospect of a nuclear decay involving ejection of a smaller nucleus made the scientific community question the "Plum Pudding" model, in which the atom was a positive sphere containing only electrons embedded within it.
Alpha particles, or helium nuclei, were put to use again in development of Rutherford's atomic model. By bombarding a gold foil with an alpha beam from a heavy isotope, the structure of the atom was analysed. It was expected that there would be small deflection of the beam, however, the detectors found that most of these particles passed through the foil, virtually undeflected. Therefore, the atom was mostly empty space. But the most striking feat was that one in 8000 alphas recoiled significantly and were detected on the other side of the foil. These alphas had come in close proximity to the positive, massive nucleus, concentrating the vast majority of the atom's mass in its direct centre. The like charges of the two "nuclei" are what caused the beam to scatter like so. This was what made scientists reject Thomson's atomic model in favour of Rutherford's, which owes its existence to helium.
The extreme and totally awesome thermodynamics and quantum mechanics of helium are very closely intertwined, and have also heralded some astonishing discoveries. It also supports my love for He-4.
From analysis of the charge density of helium-4, the most universally abundant isotope of the element, it was evident that the nature of the concentration of charge had an exponential relationship with the distance from the centre of charge in both cases, a variable which depends on quantum spin states. Simple atomic chemistry states that the helium electron orbitals, being one full shell, have zero net spin, and thus, so does the nucleus itself. The lack of spin of this isotope is what makes it highly stable when compared with similar isotopes, and its high stability along with its low energy states are what make it significant in atomic interactions. These nuclei are favourable in high-energy nuclear decays, hence why alpha particles are built the way they are. They are also a common by-product of hydrogen fusion, and in fusion research and applications, they are formed in the most energy-efficient hydrogen fusion reaction, along with an isolated neutron. In cosmology, the stability of helium explains its large primordial abundance according to our current knowledge of the Big Bang, and the ratio of hydrogen to helium in the cosmic plasma being similar to their ratios today, however failing to address the abundance of the third element, Lithium. Stellar fusion has since then produced heavier elements up to the most stable iron-56, and endothermic fusion in supernovae has produced yet heavier elements up to uranium. All elements heavier than uranium are purely synthetic.
These radical properties of helium are significant factors affecting its lack of interactivity with not only dangerously reactive chemicals, but also its own atoms. Simply put, it has the lowest boiling point of any element, assuming it obeys the properties of an ideal gas. However, the calculated melting point of helium is below absolute zero, and thus, helium cannot exhibit a triple point status. Due to the high zero-point energy of helium which is sufficient to prevent solidification, the helium nuclei would thus be predicted to form a motionless liquid at absolute zero temperature, however, it was the quantum spin alikeness of helium-4 nuclei which yielded something highly unexpected. Their symmetry of spins in all subatomic particles is what allows them, in this low energy state, to exhibit properties of bosons, and so the sample of helium becomes a quantum fluid: a Bose-Einstein Condensate, or superfluid. The asymmetry of spins in helium-3 nuclei is such that they cannot exhibit this property, unless highly pressurised.
The highly non-intuitive physical characteristics of superfluids are that they have zero viscousity, and are inclined to leveling themselves with their surroundings to form a ground state configuration. If one part of a superfluid were subject to an impulse, the rest of the system follows the same vector. Thus, a superfluid is either in an inert state of motion, or a sharply changing state. Imagining a rotating bucket of water suspended from a string, the viscousity of the water causes the drag of water molecules on the outer surface of the bucket to rotate those on the inner surface, creating a vortex. If the water were immediately replaced with liquid helium, the helium would stay steady as a rock while the bucket rotated underneath it; the string rotating above it, solely with the bucket. The assets of a Bose-Einstein Condensate also exists in superconductors, in which conducting materials exhibit zero resistance at a low temperature by allowing electronic spins to pair and cancel out. The theoretical prospect is also made out in neutron stars, where the core is thought to be a superfluid neutron mass; and in superfluid vacuum theory (SVT), in which the cosmic vacuum and dark energy is thought to exhibit superfluid properties. Thus, by studying cold helium, these theories about understanding the universe's evolution and fate are indeed very exciting and promising. At the moment, cold helium has been applied to cryogenics and cooling superconducting magnets.
Where else have we made use of helium? Balloons are a commonly known use of helium, although a larger scale use is in transport, with airships. Because helium is much less dense than air, a light container of helium is buoyant in air. Hydrogen is more so, however chemically volatile and highly explosive. Hydrogen's use in wartime airships are what causes several explosions, one of which being the Hindenburg disaster, which made the cover of Led Zeppelin's debut album.
The inert and low-density nature of helium allows it to create an inert atmosphere, which means that helium is commonly used as a stationary phase medium in gas chromatography. The speed of sound through helium is high due to the tendency for helium atoms to respond to a pressure pulse, and it is this which makes our voices high when we inhale helium, but in industrial uses, helium is often used as a fluid medium in supersonic wind tunnels, and is thus and important tool for aeronautics.
So that's why helium is my favourite element. It does more than give you a silly voice, it is on the frontiers of the new theories of science, as it has been since its discovery in the 1860's, and a useful asset to engineering. If it were not for our knowledge of the obscure applications of helium, we would be without high-speed trains, the LHC at CERN, and our explanations of many astronomical events. Helium is indeed an underrated substance, and I hope I've convinced you all that this is so. Go He!
If you think there is an element which is cooler than superfluid helium, you're a moron. Unless you can tell me why in the comments.
I can't speak highly enough of it. Wow. - gemcloben
Meh. Francium is better. - visitor
I hear helium may someday cease to exist on earth, as alone, it's too light and will all just.. Float away (I guess) I could be wrong, my science teacher isn't too reliable.
Me, on the other, appreciate Carbon, considering its willing to share its electrons with just about everything. - keycha1n
That is happening to the lightest of gases such as hydrogen, and that's because they have high speeds at the average kinetic energy of air particles, following a Maxwell-Boltzmann distribution. Those with small mass may have the escape velocity of the Earth, or greater, allowing them to escape. But this is a gradual process.
As for carbon, I like your reasoning, but as Superhyperdude mentioned, francium is good. And it's francium which is the most likely element to give away its electrons. Fluorine is the most likely to take them. - PositronWildhawk
But in terms of abundance, I think carbon wins against francium. - keycha1n
And of course, carbon forms covalent bonds, whereas francium and fluorine form ionic bonds. - PositronWildhawk
Yes, I think sharing is better than ripping it away from someone (even if its fluorine, which is begging for its electron to be taken away) how greedy, francium! I just like the idea! Haha! - keycha1n
Oxygen's pretty cool. - PetSounds
I think oxygen is the best because it's what lets us breathe on the earth. But I know you can counter this statement beciase your very smart. - Therandom
Counter the breathing of oxygen?! - PositronWildhawk
Well if I were to say anything bad about the element I breathe in order to survive, I might say that oxygen is also bad for just about everything. We need it to survive, but just like how oxidization rusts iron and causes those awkward brown spots on an apple that's left out, oxygen is also slowly killing us and breaking down our bodies. For example, if we go back to the apple, it's producing melanin (like we do in the sun) to form the brown spots to protect its vulnerable, fleshy part from dangerous substances, the dangerous substance in this case, is the oxygen. So, can't live with it, can't live without it, right?
I hope I don't come off pretentious, all of this is from a Scishow video I watched a while ago. titled "Oxygen is Killing You" or something similar. - keycha1n
Oxygen made Stevie Wonder blind. - PetSounds
I can see why you won't counter it positron. - Therandom
Hey I spent a solid five minutes typing out MY counter! - keycha1n
My personal favorite is hydrogen, it's the first element, and all others derive from it. - Turkeyasylum
Well hydrogen (like Bohr model, Sun's fuel or any star's fuel for that matter and so on) is awesome in its own ways, the same is silicon (semiconductor) in its own ways, the same is carbon in its own ways (catenation) and the same is helium in its own ways.
I really can't choose. - Kiteretsunu
I like Potassium. - Puga
I don't have a complete favorite element, but I have a bunch that I like. - CoolCat999
That's not very Noble; in fact, you're Actinide. - PositronWildhawk
Haha I get it - ProPanda
I always loved Gallium and Radium - visitor
On the other hand, when I'm reading this, Carbon and Helium are also pretty awesome. - visitor