“3-D geometry:
V S E P R, the
Theory confusing can
Seem when first faced;
So many vocab terms,
Matter-of-factual.
Summed up: electron pairs
Want their own space.”
The 2 April 2021 Twitter poem approaches the form of a double dactyl. It introduces a common theory used in introductory chemistry coursework: valence-shell electron-pair repulsion theory, or VSEPR Theory.
“3-D geometry: /
V S E P R…”
One major theme of a first-year chemistry course is molecular geometry: the shape a molecule takes. One explanation for this shape is VSEPR Theory; the acronym stands for “valence-shell electron-pair repulsion.” For this poem’s meter, the letters are pronounced individually; it’s common for a chemistry instructor to alternate between stating the letters and saying the word “vesper.”
“…the /
Theory confusing can /
Seem when first faced; /
So many vocab terms, /
Matter-of-factual.”
Learning VSEPR Theory can be challenging on multiple fronts. Not only is the general idea of a molecule’s having a three-dimensional geometry often new to students, depending on what they’ve seen in previous courses, but the specific vocabulary with which VSEPR geometries are described is extensive. Terms like “see-saw,” “linear,” “T-shaped,” and “bent” (and many others) all have particular denotations in VSEPR theory; further, many overlap with words that already have everyday meanings for students. (I used “matter-of-factual” in the single-word line here, since chemistry is generally described as the study of matter.)
“Summed up: electron pairs /
Want their own space.”
The last two lines here translate VSEPR into everyday language. Valence electrons are the outermost electrons for a given element, contrasted with the core electrons. When elements combine to form molecules, these electrons (ultimately present in a molecule as covalent bonds or lone pairs) will repel one another, meaning that the geometry that the resultant molecule adopts will be the one that maximizes distance between these electron pairs, which “want their own space.” While this phrasing is far less precise than the subsequent vocabulary we will use, deliberately demystifying the acronym is a useful first step in class.
Chemphasis 