One of the most interesting controversies I've seen about periodic table schemes is the placement of helium. It usually sits above neon as a noble gas. However, not everyone agrees with that:
"Two things are surprising about Mendeleev’s classification of the chemical elements according to the Periodic Law,” Bent writes. “One is how much of the classification has not needed revision. The other is how long the scheme’s second element has been misplaced, above neon, despite Mendeleev’s Rule of Light-Element Distinctiveness; despite his statement that the Periodic System is about atoms, not simple substances; despite classification by atomic physics of helium atoms as s2 systems (not p6 systems); despite appearance of the Left-Step Periodic Table nearly eight [now over nine] decades ago; and despite numerous implications of the LSPT that require placement of helium above beryllium.”
How you view the placement of helium (and other more difficult elements) comes down to what you believe the table represents:
- empirically-derived reactive trends of elemental substances (in which case helium above neon makes much more sense); or
- a summary of theoretically-derived electronic configuration (in which case helium above beryllium makes perfect sense).
You can see aspects of both views in the modern canonical table. It's weird exceptional cases like this that can, among other things, make chemistry such a difficult (and fun) subject to learn.
The noble gases had yet to be discovered when Mendeleev started the periodic table. Actually, the original periodic table is quite inaccurate; that it works at all is largely a coincidence that the d block has 10 elements and that the lanthanides were generally unknown (so the screwing that the f block does wouldn't crop up).
Electronic configuration is already screwed up in the periodic table more than just helium; there are several elements that don't match the expected electronic configuration, particularly in the f block. The f block itself is really annoying to actually place in the table, since there's arguments to be made as to whether La/Ac belong in the d block or if Lu/Lr move there, or if you should just cram the entire block as being a group 3 element, or if you should do something just for the lanthanides but not the actinides, etc.
Why does electronic configuration put it above Beryllium? Helium has a full first shell of electrons, and other noble gases have their subsequent shells filled with electrons, this is why they all have their property of being more or less inert. The reactive trends of noble gases aren't "emperically derived" as you say but as a result of being extremely energetically stable due to having full electron orbital shells.
EDIT: Perhaps I misunderstood and you meant that its initial placement was due to empirical data. But for good theoretical reason it has remained where it is IMO.
It's things like this that should serve as good reminders just how young our "modern existence" is, how far we've come as a species in such a short time, and (potentially) how easy it could all slip away if we let it.
Maybe that's not the best way to put it, but I hope my point comes across anyhow...
Happy Birthday, Periodic Table. May you have 150+ more...
There are now attempts to create a "periodic table" for data structures. Such a table would allow you to predict variations of data structures and the behavior of such variants. You can see such an example in page 7 of the PDF below.
That's pretty interesting, I look forward to see what comes out of this! People often tend to conflate "computer science" with "professional software development" and I admit my first reaction was "so what? I routinely use just a small handful of data structures, do we really need something like this?" but seeing it visually laid out in an easily-digestible format is somehow inspiring. From a scientific perspective I can imagine discovering more advanced structures much like "missing" elements from the periodic table.
Maybe they are using it as a mass noun or speaking specifically about the the phrase itself or the idea of data structures. Could stem from a cultural or ESOL reason.
I'm pretty under-educated on chemistry, but I read Asimov's _Search For The Elements_ a few years ago and loved it. It really demystified things.
In modern times it's easy for laymen to just wave our hands and say "yeah, we use fancy technology to do this stuff, which pretty much just treats it as magic. Asimov goes through the development of the periodic table and the discover of individual elements using classic technology.
Scanning tunneling microscope is still opaquely magic in my brain, but reading about discovering an element using technology I already understand makes even modern chemistry feel more in the realm of stuff I can get a solid grip on.
So I actually did a PhD in chemistry and just happen to work in software for reasons [0]. A thing that totally blows my mind about the periodic table and early materials chemistry is how it's in essence a derivation of "quantum mechanical" electronic structure.
One which was achieved through top-down "black box" debugging of nature on a scale too small for any human to see or touch!
Highly recommend reading Oliver Sacks' Uncle Tungsten - his tale of growing up and discovering the beauty of the periodic table with his home chemistry set. Made me appreciate chemistry and the periodic table and Oliver Sacks so much more.
I think the coolest thing about the periodic table is that it's macroscopic evidence of the discrete, particle nature of atoms and the rest of the sub-atomic universe.
Readit News
"Two things are surprising about Mendeleev’s classification of the chemical elements according to the Periodic Law,” Bent writes. “One is how much of the classification has not needed revision. The other is how long the scheme’s second element has been misplaced, above neon, despite Mendeleev’s Rule of Light-Element Distinctiveness; despite his statement that the Periodic System is about atoms, not simple substances; despite classification by atomic physics of helium atoms as s2 systems (not p6 systems); despite appearance of the Left-Step Periodic Table nearly eight [now over nine] decades ago; and despite numerous implications of the LSPT that require placement of helium above beryllium.”
https://cen.acs.org/unassigned/Reactions/97/i3
How you view the placement of helium (and other more difficult elements) comes down to what you believe the table represents:
- empirically-derived reactive trends of elemental substances (in which case helium above neon makes much more sense); or
- a summary of theoretically-derived electronic configuration (in which case helium above beryllium makes perfect sense).
You can see aspects of both views in the modern canonical table. It's weird exceptional cases like this that can, among other things, make chemistry such a difficult (and fun) subject to learn.
Electronic configuration is already screwed up in the periodic table more than just helium; there are several elements that don't match the expected electronic configuration, particularly in the f block. The f block itself is really annoying to actually place in the table, since there's arguments to be made as to whether La/Ac belong in the d block or if Lu/Lr move there, or if you should just cram the entire block as being a group 3 element, or if you should do something just for the lanthanides but not the actinides, etc.
EDIT: Perhaps I misunderstood and you meant that its initial placement was due to empirical data. But for good theoretical reason it has remained where it is IMO.
Neon has 8 electrons and 0 holes in the last shell.
Helium has 2 electrons and 0 holes in the last shell.
How do you align Helium, in the 2 electrons column over Beryllium or in the 0 holes column over Neon?
[I vote for aligning it over Neon.]
In reactions hydrogen likes to gain an electron like the halogens rather than lose one like the alkali metals.
Maybe that's not the best way to put it, but I hope my point comes across anyhow...
Happy Birthday, Periodic Table. May you have 150+ more...
Time https://www.youtube.com/watch?v=2XkV6IpV2Y0
Space https://www.youtube.com/watch?v=0fKBhvDjuy0
It's like asking a 2 year old to count way... way past 10
Made in 1977 and we can already comfortably go two orders of magnitude larger. Not bad.
Dead Comment
https://stratos.seas.harvard.edu/files/stratos/files/periodi...
They store data, so maybe it would have been nice to mention them in the paper even if it's to put them out of scope for X reasons.
Maybe they are using it as a mass noun or speaking specifically about the the phrase itself or the idea of data structures. Could stem from a cultural or ESOL reason.
In modern times it's easy for laymen to just wave our hands and say "yeah, we use fancy technology to do this stuff, which pretty much just treats it as magic. Asimov goes through the development of the periodic table and the discover of individual elements using classic technology.
Scanning tunneling microscope is still opaquely magic in my brain, but reading about discovering an element using technology I already understand makes even modern chemistry feel more in the realm of stuff I can get a solid grip on.
One which was achieved through top-down "black box" debugging of nature on a scale too small for any human to see or touch!
[0] https://news.ycombinator.com/item?id=19266614
"I saw in a dream a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper."
This is fascinating to me -- Our brains continue working during our sleep on problems we think about during our day!