“In intro chem classes, find note on /
Identification schemes rote: yon /
Wall-chart periodic /
Yields info methodic— /
Sorts matter by number of protons!”
The 3 April 2025 limerick addressed the organizational scheme used on the modern Periodic Table of the Elements (PTE), which depends on a property called atomic number.
“In intro chem classes, find note on /
Identification schemes rote…“
This limerick builds on the introductory theme of the PTE by adding a more direct explanation of how it is organized. The poem introduces how to interpret the PTE most usefully: that is, with a view towards “identification schemes rote” and other reliably predictable information that the table can provide.
“…Yon / Wall-chart periodic /
Yields info methodic— /
Sorts matter by number of protons!”
As seen last week, the PTE organizes chemical information in two dimensions (represented in the rows and columns of this famous grid).
Dmitri Mendeleev’s version of the PTE generally arranged elements in order of increasing atomic mass, which is the average weight of an element. However, he noticed that this trend, seen today in the rows, occasionally mismatched the elemental order with respect to chemical properties, seen today in the columns. In those aberrant cases, he leaned more heavily on the latter. Perhaps most famously, since he knew the patterns in both elements’ chemical behaviors and properties, he shifted tellurium, even though it had a slightly greater atomic weight, to be ahead of iodine in his ordering.
This confusion was remedied, building on the experimental findings of Henry Moseley, when the elements were instead numbered in terms of their atomic numbers, which represent the number of protons in atoms’ nuclei. In this case, tellurium has atomic number 52 and iodine has atomic number 53, so that their order is logical in both dimensions of the PTE (both row and column).
The modern PTE (the “wall-chart periodic”) provides a wealth of data (“info methodic”) and is arranged in order of atomic number (“sort[ing] matter by number of protons”).
Chemphasis 