I entered the Yale Medical Historical Library with the smell of tert-butyl methyl ether still lingering, phantom-like, from the organic chemistry lab I had just left. Tucked away in my lab notebook somewhere was the universally recognized bible of chemistry — the periodic table.

Anyone who paid a little bit of attention in chemistry can rattle off the layout of the periodic table for you. Metals on the left side, nonmetals on the right. A hard zigzag line dividing the two. Noble gases on the far right. Transition metals spanning the center. Rare earths — the lanthanide and actinide series — expanded below. But what I saw in the Medical Historical Library looked nothing like the simplified design we use today.

“The History of the Periodic Table in the Twentieth Century,” curated by Charlotte Abney Salomon GRD ’19, is composed of fewer than twenty objects, and yet it succinctly illustrates the long, nonlinear path our current periodic table has taken in the past 150 years.  The small sample of items is part of graphic designer William Drenttel’s lifetime collection of over 200 English language books, pamphlets, advertisements, and collectibles.

The first object in the display is not a depiction of the periodic table at all. Rather, it is a commemorative stamp honoring Dmitri Mendeleev, the father of the periodic table. Though others organized the elements in a table of rows and columns, Mendeleev was the first to order them by weight and reactivity, leaving blanks in order to maintain consistent trends. By doing so, he predicted the existence of elements that would not be discovered until later on.

Farther down are open spreads of books from the 1900’s illustrating early attempts at periodic organization. As chemistry advanced, scientists looked for new ways to organize more complex knowledge. “Periodic triads” grouped three elements of similar reactivity together. Other items showed off more esoteric designs: One periodic table from the University of Minnesota in 1939 uses a branching design, starting with only hydrogen and helium at the top and widening as it progresses down the page, making room for the transition metals and the lanthanides and actinides. A French commemorative medallion has the elements etched in concentric circles.

These designs first struck me as whimsical, but after a moment of thought, I started to see their logic. After all, one layout of the periodic table, as long as it is accurate, is not necessarily better or more scientific than the rest. I had never questioned how or why our periodic table looks the way it does until I was face to face with a host of equally valid designs.

The periodic table finally began to coalesce into a standardized format around the 1960s, which the second display case illustrates. The black and white Welch Periodic Chart of the Atoms from 1959 depicts each element in an individual box, and the layout is more reminiscent of our modern day periodic tables. But the design is still not optimal: Rather than leaving a gap for the transition metals, however, the bottom rows wrap under themselves to accommodate all the elements.

On a table, in a children’s book from the 1960s seems like the modern version, but upon closer inspection, I noticed that noble gases are placed on the left side instead of the right! But such a minor difference in the overall design set off a cascade of questions, “Why are our noble gases on the right side instead of the left? Or instead of the middle of the table, so that the elements increase in reactivity towards the edges?” It’s wonderful and a little sad to realize that even science, the bastion of objectivity and empiricism, is shaped by subjective cultural trends.

Then, the exhibit abruptly leaps from historical periodic tables to today’s table, as seen in pop culture. All of a sudden, the books yellowed by age are replaced with a brightly colored assortment of everyday objects, including a mug, a tie and two recent magazine advertisements, all with the periodic table printed on them. The current version of the periodic table has become a cultural symbol of scientific thinking and an easily recognizable method of grouping items — from television to mixed drinks — by different criteria and breaking those groups down to their basic elements. Science, too, leaves its mark on popular culture.

Though the exhibit does not demand to be noticed — indeed, it’s easy to miss unless you specifically peer down into the cases — it tells a powerful story with a small collection of carefully chosen pieces. Chemical knowledge has only appeared in this specific physical format for 50 years. And I didn’t realize it until now.

It’s so easy to take our version of the table for granted when it’s all we have studied, but the theories and tools we have today came about through incremental changes over time. “The History of the Periodic Table” reminds us that science is a process, not a result.