It’s Elementary, My Dear Mendeleev…

Posted By on September 12, 2013 in News |

One of the great pleasures of having a high schooler in the house — and no, I’m not being facetious — is being reminded of my favorite subjects, minus the adolescent drama and classroom tedium.

Case in point: the periodic table.

You may remember the periodic table as an arrangement of all the known elements in colorful little boxes, complete with maddening abbreviations and tiny numbers. There’s a good chance a poster of it hung on the wall of your chemistry lab. On the other hand, you may not want to remember it, if chemistry was a hair-pulling nightmare for you — or, even worse, a big bore.

I liked chemistry. I’m not sure why, but I did. Which means I have a soft spot for the periodic table.

So when our little Nina came home from her first day from school, plopped down on the sofa with an operatic air of exhaustion, and asked us to quiz her on it, we were only too happy to oblige.

Each element in the periodic table has a symbol, usually a one or two letter abbreviation, the first letter always being capitalized. That white stuff in your salt shaker, for instance, is a chemical compound called “sodium chloride,” a combination of Sodium (Na) and Chlorine (Cl).

First year chemistry students are often tasked with memorizing the symbols of all the common elements — setting aside, for the time being, exotics like Astatine (At), Seaborgium (Sg), and Ytterbium (Yb).

Some of the symbols are pretty straightforward. It’s not too hard to remember that Hydrogen is H, or that Oxygen is O.

But why should Gold’s symbol be Au? Or Lead’s, Pb? And what did poor old Tin ever do to deserve the bizarre moniker Sn?

The answer lies in the history of the periodic table, which is really a work-in-progress that dates back thousands of years.

We tend to associate the table with the scientific discoveries in the 19th century that gave it its familiar shape. If you were paying attention in chemistry class, the name Dmitri Mendeleev will probably ring a bell. Mendeleev was the Russian who, in 1869, proposed a table of known — and unknown — elements, arranged in a series of columns and rows that corresponded to their atomic weight and their valance; i.e, the mass of their atoms and the kind of chemical bonds they liked to form.

Other scientists had drawn up tables of the elements, but none of the other tables accounted for the mysterious similarities among certain elements: why, for instance, Helium and Neon were basically inert gases, whereas Lithium and Sodium were highly reactive metals.

What made Mendeleev’s table superior to his colleagues’ proposals, some of which were quite similar, was that Mendeleev not only organized all of the known elements, which at the time, numbered around sixty, but also predicted elements, based on blank spaces in the table, that weren’t yet known. As, one by one, the predicted elements were indeed found in laboratories around the world, Mendeleev’s table came to be accepted as standard.

Standard, but not complete. At the moment, we’re up to 118 elements, and counting. And, truth be told, not even entirely correct. Subsequent advances in chemistry established a more accurate organizing principle for the periodic table than atomic weight. What really separates the elements isn’t weight, but rather how many protons are in their nuclei.

Of course, protons hadn’t been discovered in Mendeleev’s time. So I think we can give him a free pass on that front.

But back to the table’s strange symbols. As I said, we tend to associate the periodic table with the late 19th century, but by the time Mendeleev rolled around, metalworkers and alchemists had been separating lumps of this from bits of that for millennia. The Romans put their stamp on this ancient knowledge with names like “aurum” for gold; “plumbum” for lead; and “stannum” for tin. Thus: Au, Pb, and Sn.

As the periodic table sailed into the 20th century, and scientists probed ever deeper into the mysteries of Mendeleev’s columns and rows, new theories arose to explain the seemingly magical “periodicity” of the elements; i.e., why elements combined — or didn’t — in such highly predictable ways. This led to the discovery that elements in the same column of the table had a similar configuration of electrons. The behavior of those electrons, and the problem of zeroing in on them, led, in turn, to the field of quantum mechanics.

I’m not going to lie. It’s not as if all of this information came flooding back as Nina rattled off the symbols for Silver, Zinc, and Argon. I had to read up on the periodic table in order to write this piece about it.

But I read up on it with gusto, at my own pace, following my curiosity to its natural depth. Which begs the question: why didn’t I learn it that way the first time?