There are only a few developments that have organized the way we see the world. There is the classification system of the life sciences, which separated the world into the animal, mineral and vegetable kingdoms. There is the Constitution of the United States, which created a delicate system of checks and balances. There is double-entry accounting, which made modern bookkeeping possible and sometimes is credited with giving flight to capitalism. There is the Baseball Rulebook, which sets forth the infield-fly rule.

And there is the Periodic Table of the Elements.

It almost certainly has escaped your notice but this month is the 150th anniversary of this key to how the known world (and beyond) is constructed. It has many progenitors, but the principal one is a Russian chemist named Dmitri Mendeleyev, who had a prodigious Old Testament beard, who was shaped by the liberal notions that were in the air of Tsarist Russia in the years between the Decembrist uprising of 1825 and the assassination of Alexander II in 1881, and who was energized by a conference of chemists in the southern German town of Karlsruhe two months before the election of Abraham Lincoln. In March 1869 he crafted a graphic tool that, as Paul Strathern explains in his landmark 2001 “Mendeleyev’s Dream,” performed the astonishing achievement of having “classified the building blocks of the universe.”

The Periodic Table was set out by Mendeleyev before the discovery of electrons, so the irony — perhaps the genius — of this tabular display of noble gases and ignoble substances is that a table based on atomic weights could predict interactions between elements even before the discovery of the structure of the atom. That was either a stroke of luck, a stroke of genius or, perhaps antithetical to the entire ethos of science, a stroke of providence.

The bane of high-school chemistry students, the Periodic Table is remarkable for predicting elements that would in time fill in its own gaps — almost like a jigsaw puzzle whose missing pieces would eventually be discovered to be in the box or on the floor. It is even more impressive because jigsaw puzzles come with an image of how to fill in the blanks while the Periodic Table had no such assistance.

Actually many of those new elements will be created by the collisions of a beam of nuclei with a target, a process known as multi-nucleon transfer reactions. “Their nuclei wouldn’t fuse completely, but a chunk of one might break off and glom onto the other,” according to an account published this year in Science, the journal of the American Association for the Advancement of Science. “Depending on the size of the chunk, scientists might even leap to much higher element numbers instead of inching along one atomic number at a time.”

These high-number elements won’t actually be new but instead simply substances scientists haven’t discovered yet or, in the case of 24 of them already identified, artificially created — the physical-science analogue of the aphorism often attributed to the Irish poet William Butler Yeats: “There are no strangers here, only friends you haven’t met yet.”

Mendeleyev’s creation — the widely known graphic that places Magnesium (Mg) under Beryllium (Be) and Chromium (Cr) beside Manganese (Mn) — was less the product of conscious invention than remorseless necessity.

In 1869 — remembered mostly for the opening of the Suez Canal and for the completion of the Transcontinental Railroad in Utah, two achievements that tied the world more tightly together rather than separating its elements — the Russian scientist held the position of professor of chemistry at St. Petersburg University. There he faced the challenge of teaching a required course in inorganic chemistry. The most useful instruction books were badly translated European texts, so he vowed to write his own version. Halfway through, Mendeleyev faced a scientific challenge:

“I had to set up simple bodies in some kind of system so that their distribution was not governed by accidents, as if by instinctive guesses, but by some definite exact principle.”

The result is history or, in the manner of the structure of the university and of the universe, chemistry — a format considered, Princeton historian Michael D. Gordin argued in his 2004 volume ‘’A Well-Ordered Thing,’’ as ‘’one of the most useful tools in chemistry.’’

Indeed, modern chemistry would not be possible without the Periodic Table, as much a roadmap to the far reaches of the universe as it is a gazetteer to the known world. As a result, we remember Mendeleyev as one of the great map makers of all time, the laboratory version of Gerardus Mercator, whose landmark 1569 cylindrical projection laid out the known and unknown world for others to explore — or as the scientific version of John Milton, who in Line 26 of his classic “Paradise Lost” set out to “justify the ways of God to men.” Mendeleyev explained the ways of the universe to us all.

David M. Shribman is executive editor emeritus of the Pittsburgh Post-Gazette and a nationally syndicated columnist.

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