Theodore Gray’s literal periodic table of the elements
PHOTO: MIKE WALKER
The United Nations has declared 2019 the International Year of the Periodic Table of the Chemical Elements (www.iypt2019.org) and thus the 100th anniversary of the founding of the International Union for Pure and Applied Chemistry. The organizing committee stated: “The periodic table of the chemical elements is one of the most important achievements in science and captures not only the essence of chemistry, but also physics and biology.” Indeed, many non-scientists recognize the periodic table by the characteristic shape of its boundary, but within that boundary there are many aspects of science beyond chemistry. Science is about the interplay of experimental results and theory. A sufficient number of elements had to be discovered and their properties and reactivity understood before systematic trends could be derived. Science is also fundamentally about making verifiable predictions. Part of the success of Dmitri Mendeleev’s original table, published in 1869, was that it left gaps for placement of undiscovered items. Mendeleev predicted some properties of these elements and sparked a chain of scientific hypothesis tests. The structure of the periodic table was later understood to be quantum mechanical. The elements themselves are created through a complex chain of star nucleosynthetic processes, and the limit of the periodic table – the search for stable superheavy elements – tests the limits of experimental atomic physics.
A large periodic table is often displayed in classrooms (not just chemistry classrooms), but often too high up on the wall for anyone to see more than the element symbols and ordinal numbers. Periodic tables hung this way really serve as banners or flags, telling anyone who walks in that “we are doing science here”.