Blogging the Periodic Table
For those of us who care about things like beauty in science, we're witnessing a special moment in periodic table history—though disenchantment will come soon enough.
In April, a joint Russian-American team announced the creation of a half-dozen atoms of Element 117, named (for now) ununseptium. Its creation filled a blank on the table that was ugly for two reasons. For one, all the elements through 116 had already been created or discovered—and so had element 118. (For technical reasons it's easier to create even-numbered elements like 116 and 118.) That left a gap at 117, which violated a natural sense of progression. It's true that, historically, chemists didn't discover the other elements in any kind of order. But aesthetically, the gap at 117 was off-putting.
The gap was also galling because the periodic table stood just one box short of completing its seventh row—ununseptium squares off that bottom row. Things just look better. And what's more, the beauty and tidiness here isn't some arbitrary human convention, because the width of the table is fixed by nature, not by what looks good to us. Atoms of Element 118 fill an outer shell with electrons, creating a special type of element called a noble gas. Noble gases are natural turning points on the table, ending one row and pointing to the next. Everywhere in the universe, the periodic table has the same basic structure. Even if an alien civilization's table weren't plotted out in the castle-with-turrets shape we humans favor, their spiral or pyramidal or whatever-shaped periodic table would naturally pause after 118 elements. No matter how you reckon it, 118 is a special number among elements, as universal as π. With the creation of element 117, scientists have reached a milestone.
The beauty is all the more poignant because it will not last. The best element-making labs in the world are located in Berkeley, Calif.; Darmstadt, Germany; Dubna, Russia; and Tokyo. Their scientists might appreciate the tidiness of the current periodic table, but they're already working to ink in the first boxes of the eighth row, which will leave little jagged sawtooths stuck at the bottom of the table. The science behind the boxes will be grand. The resulting picture, less so.
But, you might protest, that's just the start of another adventure. Scientists will fill the eighth row as well, and then we'll get to experience this pleasure all over again, and with a bigger family of elements. Perhaps. But the unusual arithmetic of the periodic table will make things much harder. Notice that the second and third rows of the table double back after eight elements. The fourth and fifth rows have 18 elements, and the sixth and seventh rows (when you count the double strip hanging below the table) have thirty-two. The periodic table gets wider as you move down. Filling the eighth row will require 50 new elements, all the way to 168. Before ununseptium, no one had created a new element in six years. So assuming our technology improves at the same rate it has in the past, it could take hundreds of years before Row 8 fills out.
And that's assuming we even can fill Row 8. Periodic table science could butt up against some strict limits of how large atoms can get, and butt up against them well short of element 168.
There are a few simple reason for this. The first and more practical consideration is that atoms much bigger than 118 are incredibly hard to make. The second reason is more subtle and theoretical. Atoms consist of a positive nucleus and negative electrons flying around outside it. Electrons closest to the nucleus feel a strong negative-on-positive tug, and the bigger atoms get, the bigger the tug. In really big atoms, electrons whip around at speeds close to the speed of light. But Einstein's theory of relativity says nothing can go faster than light. If you do the math, electrons could suddenly violate the laws of relativity around element 137, untriseptium. This is just a theory—perhaps a future team of Japanese-Russian-America-German scientists will bust Chuck-Yeager-style through the 137 barrier. (And some scientists do argue that any relativistic limit would come much later, at element 173.) Regardless, though, these elements would be very difficult to create, and such difficulties could cap the periodic table long before element 168.
Which means that the periodic table of the next few years could be the only "complete" and perfectly squared-off version humans will ever know—a beauty we should appreciate all the more because we know it's fleeting.