The seventh row of the periodic table is now full | Hacker News Reader

The seventh row of the periodic table is now full

iupac.org

133 pointssrikar32 comments

See also the hypothetical Island of Stability. https://en.wikipedia.org/wiki/Island_of_stability

That's as good as SciFi at the moment, no?

One of the scientists working on these elements commented on the Island of Stability on Reddit. "While the next "magic" number of protons is predicted to be 114, 120 or 126, we are still too far away from the next extra stable configuration of neutrons."

https://www.reddit.com/r/science/comments/400w7k/science_ama...

Here's the current full table (with the seventh row complete):

https://upload.wikimedia.org/wikipedia/commons/3/3d/Discover...

Why are elements 57 and 89 shaded white?

Those are placeholders for the two rows (lanthanide and actinide series) below the main table.

To be clear—it's because the periodic table is actually shaped like this: http://www.chemistryland.com/CHM130W/03-BuildingBlocks/Chaos...

I think folding the periodic table like we do makes it much harder for children to understand valence levels. To quote Wikipedia (https://en.wikipedia.org/wiki/Atomic_orbital):

> The "periodic" nature of the filling of orbitals, as well as emergence of the s, p, d and f "blocks", is more obvious if this order of filling is given in matrix form, with increasing principal quantum numbers starting the new rows ("periods") in the matrix. Then, each subshell (composed of the first two quantum numbers) is repeated as many times as required for each pair of electrons it may contain. The result is a compressed periodic table, with each entry representing two successive elements:

   1s
   2s                                                  2p  2p  2p
   3s                                                  3p  3p  3p
   4s                              3d  3d  3d  3d  3d  4p  4p  4p
   5s                              4d  4d  4d  4d  4d  5p  5p  5p
   6s  4f  4f  4f  4f  4f  4f  4f  5d  5d  5d  5d  5d  6p  6p  6p
   7s  5f  5f  5f  5f  5f  5f  5f  6d  6d  6d  6d  6d  7p  7p  7p

That's a table that lets you understand things.

---

...though, taking it absurdly literally, imagine a world where our taxonomy of "elements" was constructed like this, rather than by proton-counting. Hydrogen and Helium would be different isotopes (prototopes?) of the same element. Fluorine and Neon would be the same "element", too. We'd get a strong intuitive sense, even from first hearing about chemicals as children, that certain "elements" have volatile behaviors that can be explained by what they're paired with—Fluorine being so reactive because it's the -1 "prototope" of Neon and really wants to oxidize something so it can have Neon's full valence shell, etc.

Or, to go further, imagine we divided our chemical taxonomy by entire subshell—that we just had elements called "1s", "4f", etc. with "prototopes" for uranium, actinium, etc., with their distance from an empty/full subshell represented in their names. It'd be immediately clear what makes certain elements semiconductors: silicon's name would be "3p±4" and, well, that's all you need to know about silicon.

I think some would say that the "actual" shape (and possibly easier to learn) is more of a spiral than a table format.

http://i.imgur.com/QOoKC1a.jpg

The periodic table is a human construct, so its "actual shape" is not in dispute.

(And why is iron below helium, neon, and argon? That makes no sense at all.)

That may be true, but even models can have a closer or less close relationship to the thing they model and modeling 3D orbits around a central nucleus is quite hard in a rectangular mapping, the spiral (even if this one may be flawed) seems to show more clearly that the space in orbits further out will accommodate more electrons.

What do you mean by "modeling 3D orbits"? Because that's not what the periodic table is doing. It's telling you which quantum numbers are in use. The rectangle is extremely good at that (with a couple minor simplifications). The problem with the spiral is that it will have the same discontinuities as the rectangle, because each angular momentum number has two more magnetic quantum numbers than the previous.

Or, in other words, the disadvantage of putting more space farther out is that you lose the most important property of the periodic table, which is the groups.

2n^2, that the underlying reason for that equation is a quantum effect is not required for the basic understanding that 'further out' means 'more room'. That in the end the equations are about energy levels rather than space does not matter when you're trying to remember what the periodic table looks like, it's a useful mental construct, even if it is fundamentally in-accurate.

More like a bulged spiral.

http://www.av8n.com/physics/periodic-table.htm

Valence levels pretty much become meaningless after the d block. In the d block, elements lose their electron configuration patterns I'm nontrivial ways that make periodic arrangement less useful.

What are the chances of any more non-radio active elements to be found? Is the current knowledge sufficient to state this will never happen or is there still a very small chance?

https://en.wikipedia.org/wiki/Island_of_stability

> Although predictions of the exact location differ somewhat, Klaus Blaum expects the island of stability to occur in the region near the isotope 300Ubn.

> Estimates about the amount of stability on the island are usually around a half-life of minutes or days, with "some optimists" expecting half-lives of millions of years.

It is currently not expected that there will be any stable nucleon configurations between lead and small neutron stars (which cannot really be considered "elements"). On the other hand, we don't know how well the current theories describe elements heavier than the ones we managed to generate (not least because we cannot actually produce much heavier elements yet).

Also how close is particle physics to generating anything in the eighth or higher periods? Is the leap from 118 to 119 greater than 117 to 118?

Element 115 just must be called Elerium!

http://www.ufopaedia.org/index.php?title=Elerium-115

In other names that are unlikely to happen, ununoctium would be a pretty good candidate to be named "unobtainium".

Qualifications include the kind of similar name, its half-life of less than a millisecond, and the bizarre properties it's hypothesized to have if you somehow put enough of it together to have physical properties.

Isn't that about on the level of calling an actual piece of software "Foobar"?

That piece of software exists, it's a popular audio player called foobar2000 https://www.foobar2000.org/

That's why I asked that. Their's a crap name.

What's the in-joke with the temporary names? (ununtrium, ununpentium ...)

https://en.wikipedia.org/wiki/Systematic_element_name

Pretty sure they're just sort-of-latin for 113-ium, 115-ium etc.

I was mostly thinking of the unun part?

"Ununpent" = "one-one-five"

ununtrium (element 113)

> un un tri

> one one three

ununpentium (element 115)

> un un pent

> one one five

etc.

One is "unum" in latin.

Thanks, that was what I was missing. I figured it was the un- prefix, which means something like non-existing. (https://en.wiktionary.org/wiki/un-#Prefix)

The temporary "systematic" names exist due to disputes over element names in the past. Standard practice is that the discoverers of new elements are allowed to recommend names; but there have been arguments over who synthesized a new element first, resulting in American and Russian physicists using different names. The rule now is that the systematic names get used until IUPAC has time to authenticate a discovery and establish whose name will be used.

There is one in-joke I've heard about systematic names, though: What's the symbol for Unhexhexium? (Answer: "Uhh...")

Reply on news.ycombinator.com