Here at Top Comments we strive to nourish community by rounding up some of the site's best, funniest, most mojo'd & most informative commentary, and we depend on your help!! If you see a comment by another Kossack that deserves wider recognition, please send it either to topcomments at gmail or to the Top Comments group mailbox by 9:30pm Eastern. Please please please include a few words about why you sent it in as well as your user name (even if you think we know it already :-)), so we can credit you with the find!
I have written before about superheavy elements (such as this diary). As a (now retired) chemist, I’m ambivalent about the effort put into making such elements. They are not found in nature, though they may be produced during supernovas. They tend to have very short half-lives (on the order of milliseconds), after which they decay into lighter elements by shedding alpha and beta particles. With such short half-lives, it’s nearly impossible to do any actual chemistry with them. However, producing such elements reveals details of the forces that hold together the protons and neutrons in the nucleus. In recent years, the periodic table has been extended to element 118, called oganesson (symbol Og), which completed the table’s seventh row. What this means is that producing still heavier elements will start the eighth row of the table.
Modern periodic table, mostly legible on blow-up.
While chemical properties for such short-lived elements are nearly impossible to determine, certain physical properties are quantifiable, such as the new element’s spectrum. When atoms of an element are put in a discharge tube, and electrons shot through it, exciting the atoms present, they produce a spectrum of sharply defined lines with precise wavelength, characteristic of said element. The light is caused by electrons in the atoms jumping from one atomic orbital to another; the energy of the emitted photon is equal to the difference in the energies of the two orbitals involved in the transition. Theorists can predict what the spectrum might look like, but you can’t know for sure what it will look like until you do the experiment.
One question that’s high in my mind about elements in the eighth row of the periodic table has to do with where electrons end up as we proceed across the eighth row. If you had a chemistry class that covered atomic structure, you’ll likely know that atoms have electron shells, and that each shell has a certain number and type of orbitals. Orbitals are where an atom holds its electrons, and each orbital can hold two electrons at most. The lowest energy shell has only one orbital, and it’s an s-type orbital, which is spherical (1s). The second shell has four orbitals, one s-type (2s), and three p-type (2p). The p-type orbitals are shaped sort of like dumbbells, as depicted in the second row of the table below. The third shell consists of a total of nine orbitals: one s-type (3s), three p-type (3p), and 5 d-type (3d). The d-type orbitals sort of look like cloverleafs. For those of you who are good at spotting patterns, you may have noted that the number of orbitals in the shells so far is equal to the square of an integer: 1st shell 1; 2nd shell 4; 3rd shell 9. This pattern continues to the 4th shell, which has 16 orbitals, consisting of 1 s-type, 3 p-type, 5 d-type, and, now, 7 f-type orbitals, whose shapes are reflected in the last row of the table below.
The shapes of atomic orbitals. Starting at the top is the spherical s-type orbital; there is only one s-orbital in a
The modern periodic table reflects atomic structure in its arrangement. If you look at the top row of the table, there are only two elements in it: Hydrogen and helium (H and He). These are the only two elements possible if electrons are limited to the first shell, with its single orbital. The second row has eight elements in it, reflecting the filling of the four orbitals in the second shell, with 2 electrons per orbital. The order of orbital filling gets complicated after the 2nd shell, but be aware that the sections of the periodic table reflect which subshell (s, p, d, or f) is in the process of being filled. The first two columns are called the s-block because the s-orbitals contain the outer electrons. The six columns on the right are called the p-block because the outermost electrons are in the p orbitals of the shell. The ten columns placed between the s-block and the p-block is called the d-block because the d orbitals are the ones in the process of filling. Then there are those two rows at the bottom of the table, 14 elements long,* that actually get wedged into the space between the s-block and the d-block in the last two rows of the table above. You guessed it: these rows are the f-block.
For me, the exciting thing about venturing into the 8th row of the periodic table is that we may see the involvement of the first g-type subshell (5g) in the electronic structure of the atom. A g-type subshell has 11 orbitals, and so can contain as many as 22 electrons. However, we won’t know if, or how, the g-orbitals become occupied until scientists make and study elements beyond element 118.
So how are such elements made? You ram ions of one element into atoms of another, where the sum of their atomic numbers adds up to an element that hasn’t yet been created, and pray they hold together long enough to be detected as a single atom. (The atomic number of an element is equal to the number of protons it has, which defines the identity of the element.) However, once you get past atomic number (Z) 118, there is a practical problem. Up to this point, everybody’s favorite element to ram into the target of heavier atoms is calcium, atomic number 20, because it’s stable and easy to handle. Element 118, oganesson, was produced by ramming calcium ions into element 98, californium: 20 + 98 = 118. However, once you get past californium, it’s hard to obtain enough of the element to perform the experiment on, and, as always, the half-lives of these elements start getting inconveniently short.
The new step forward featured in the linked article is that they have switched from calcium to titanium (atomic number 22) in order to try to get to element 120.
“The titanium beam is really hard to make,” says Gates. Titanium’s melting point is almost 1,700 ºC, more than twice calcium’s. “To make a titanium beam, you have to heat it enough to get ions to evaporate off, and you’re putting this a couple inches from things that have to be cooled to liquid-helium temperatures,” she says.
There are many additional unknowns, such as optimal energies required to make the desired element. There are no good theoretical predictions in this new row of the periodic table. From my perspective, to see electrons in the 5 g subshell, you’d have to get beyond element 120, to, say, element 125 or so, and that’s going to require something heavier than titanium. But I’m sure they’ll get there eventually. I just hope I’m still alive and sentient when it happens.
Comments are below the fold.
*If you actually count the number of columns in these lowest rows, you’ll see that there are actually 15 rather than 14. That’s an error in the table that arises because, in order to create the gap in the d-block into which the f-block would fit, they removed one element from the d-block and added it to the f-block. No image you find on the internet is perfect.
Top Comments (July 28, 2024):
From fromberkeleytocville:
This comment by Laurence Lewis in their diary today is one of the most succinct summations of Republicans vs Democrats I've ever seen and it deserves to be remembered and used by all of us.
They offer whimpering anger, cruelty, bullying, and greed. We offer the strength of community, kindness, and hope.
From belinda ridgewood:
Mother Mags posted a diary about a weird Arizona GOP conspiracy theory about Joe Biden being replaced by a double, in which he recalled the old "Paul is dead" Beatles CT. Elwood Dowd shared that he has a very different theory that explains everything!
From meadowmist:
Continuing Azubia's excellent discussion from one who knows diary yesterday, here's another comment from them that really, as Bill Blondeau says, eloquently sums up where we are right now.
Top Mojo (July 27, 2024):
Top Mojo is courtesy of mik! Click here for more on how Top Mojo works.
