For those of us that write about the periodic table for a living, the gap at 117 was doubly galling. First, every element through 116 had already been discovered, as well as element 118. (To be accurate, the elements through 92 had been discovered, and the elements after that created, in a lab, since the days of getting your fingernails dirty looking for new elements in nature ended about 1930. The ultra-heavy elements never existed before people created them, unless in the labs of alien scientists somewhere distant.) Anyway, the gap at 117 violated a sense of order, since we like things to start at 1 and progress to N without skipping around. That for technical reasons it’s easier to create even-numbered elements like 116 and 118 couldn’t salve our aesthetic sense that something was somehow wrong with there being a gap for ununseptium.
Second, the gap was galling because the periodic table was just one box short of completing its seventh row. Because of the way electrons stack themselves inside atoms, the table always has eighteen columns; but the number of rows changes, and grows fractionally longer with each new element. And it was frustrating (at least for some of us) to be sitting on 6.96875 rows (6 and 31/32) for years, so close to 7.00000. Ununseptium fulfills the table, squares off the bottom row. It just looks better now.
We can find even more satisfaction because the beauty here isn’t arbitrary human beauty. The tidiness doesn’t depend on our senses or our accidental circumstances on Earth. For example, it’s human convention to celebrate turns of millennia or 100th wedding anniversaries because we like to see zeroes. Really, that’s just an accident of our base-ten counting system, because numbers like 200 and 2,000 look good in that system—those pleasingly geometric circles (or at least ovals) stacked at the end, and the sense they give of having turned from one era to another. But if we had seven fingers, 100 would be written as (in base-seven counting) “202”; 1,000 would be “2626”. Had we thirteen fingers, they’d respectively be “79” and (because we’d need more digits than 0 to 9 in a 13-digit system) “5BC”. So there’s nothing inherently special about those numbers, just the numerals.
The beauty of the periodic table isn’t constrained by our metatarsals. Everywhere in the universe, the basic periodic system is exactly the same. Perhaps not jotted down in the castles-with-turrets shape we humans have come to favor, but in every civilization that ever discovered the periodicity of atomic structure, the spiral or chart or hologram or whatever would naturally pause after 118 elements, would rest as a cycle completes itself. No matter how someone counts or reckons, 118 is a special number among elements, a millennial anniversary built into nature, as universal as π.
But, you might protest, it’s just another great adventure. Surely we’ll fill the eighth row as well, and then get to experience this pleasure all over again, only with a far bigger family of elements. Perhaps. But the unusual arithmetic of adding elements to the periodic table will make things much harder. Notice that the second and third rows of the table double back after ten elements. The fourth and fifth rows have eighteen elements, and the sixth and seventh rows (when you count the double strip along the bottom of the table, lanthanum to lutetium and actinium to lawrencium) have thirty-two elements. In other words, the periodic table gets wider as you move down, like those dinner tables with planks you insert to extend them around Thanksgiving. (You can see a picture of the daunting progression here.) For these reasons, the eighth row will require adding fifty new elements, all the way to 168. Before ununseptium was added, no new elements had been created in six years, and ununseptium took over a decade of work. That means it could take hundreds of years before row eight fills outs.
And that’s assuming it’s even possible to fill row eight. You can easily assure yourself immortality (as an ass) by declaring something impossible in science, but periodic table science seems likely to butt up against, very soon, some strict limits of just how large atoms can get, limits that start to become important thirty squares short of 168. There’s a simple reason why, related to Einstein. If you remember your nuclear anatomy, atoms are made of positively charged protons and neutral neutrons in a nucleus, as well as negative electrons flying around outside. The electrons don’t float freely, however; they’re arranged in concentric shells, shells nested one inside the other. The innermost electrons fly faster than the outermost ones because the innermost ones are nearer the nucleus and therefore feel a stronger negative-on-positive tug.
When atoms get really big, they have lots of protons and accumulate a lot of positive tug; so those electrons begin whipping around at speeds close to the speed of light. But of course Einstein’s relativity says nothing can go faster than the speed of light. And if you do the math, electrons would suddenly violate the laws of relativity right around element 137, untriseptium. This is just a theory—perhaps a future team of Japanese-Russian-America-German scientists will bust Chuck-Yeager-style right through the 137 barrier. But for right now it looks awfully daunting, and it could cap the periodic table long before element 168. Which means that the periodic table of the next few years could be the only perfectly squared-off version humans will ever know.
