“Our molecule’s geometry
As sketched-out: asymmetric;
We also note an (overall)
Lopsided charge electric.
Electrostatic map thus shows,
Through densely different hues,
Unequ’lly shared covalent bonds:
Polarity ensues.”
The 2 April 2020 poem describes an electrostatic potential map, a visual, color-coded tool with which chemists can quickly assess the variation of electronegativity for the atoms in a given molecule. Understanding a molecule’s polarity (or lack thereof) is an important step in assessing its properties and reactivity. Determining whether a species is polar or non-polar overall can also be achieved via consideration of whether its covalent bonds are polar or non-polar.
“Our molecule’s geometry /
As sketched-out: asymmetric; /
We also note an (overall) /
Lopsided charge electric.”
In considering a molecule’s polarity, we consider its geometry (shape) and its overall charge distribution; “sketch[ing] out” a molecule allows us to assess these properties quickly.
Water, for instance, is famously polar. It contains an oxygen atom and two hydrogen atoms, arranged in a V-shape. The oxygen atom is highly electronegative: it strongly attracts its electrons to itself. The oxygen atom takes on a partial negative charge. Each O-H bond is “polar covalent” and the molecule’s charge distribution is, overall, “lopsided”: the electron density is shifted towards the oxygen atom. Non-polar molecules can have bonds in which atoms share their electrons equally via non-polar covalent bonds (such as H2, in which each hydrogen atom behaves identically). They can also contain polar covalent bonds, if the symmetry of the molecule means these effects cancel one another out overall (as in CO2, where the oxygen atoms are linearly arranged on either side of the central carbon atom).
This particular poem describes an asymmetric molecule with polar covalent bonds.
“Electrostatic map thus shows, /
Through densely different hues, /
Unequ’lly shared covalent bonds: /
Polarity ensues.”
For the molecule described here, an electrostatic potential map would show high electron density (electronegativity) in red and low electron density (electropositivity) in blue: “densely different hues.” Lines 1-4 previously established that the molecule does not have a symmetric geometry. Our takeaway is that our hypothetical species will have polar covalent bonds and be polar overall: “polarity ensues.”
The inspiration for this poem was the similarity in sound between the final line and “hilarity ensues,” a common trope in entertainment writing.
Chemphasis 