Somewhere on the wall of every high school chemistry lab hangs a Periodic Table of the Elements. I need only close my eyes to summon up the Periodic Table that hung in my own high school lab -- a giant, colorful thing with the symbols of the elements printed in bold black letters on sturdy fabric, published by Welch Scientific, if I remember rightly.
I was not an enthusiastic student of chemistry, but when I looked at the Periodic Table I knew I was in the presence of a fundamental mystery. The way the elements fell into place, in ranks and rows according to their properties -- well, it was like music.
Why should the stuff of which the world is made be replete with patterns, harmonies, and cadences? On the left, in column 1, the alkali metals -- lithium, sodium, potassium, and their heavier cousins (keep them away from water, our teacher stressed). On the right, in column 18, the noble gases -- helium, neon, argon, krypton, and xenon (safe and sane, completely inert). And bracketed between, like substances neatly arranged on a pharmacist's shelves, the 92 naturally occurring elements, and a partial row of unstable heavier elements added by those modern alchemists, the nuclear physicists.
There were puzzles aplenty in the table to intrigue the curious student. Why did the gaseous elements cluster at the upper right of the chart? What was liquid mercury doing down there in the middle of the chart surrounded by solids? Why did copper, silver, and gold, among the few elements known since ancient times, have a column of their own?
In short, what was the magic behind the music? What was the instrument whose tuning made the harmonies? The mysteries were soon unraveled by our teacher, who introduced us to the theory of atomic structure and chemical valency. It would be hard to describe the excitement that accompanied the realization that the amazing diversity of the world of matter -- the reactiveness of the alkalis with water, the inertness of the noble gases, the slipperiness of mercury, the solitariness of gold -- all of this and more, could be explained by a theory of almost childlike simplicity.