Is the letter sign required for single letter elemental symbols that have a sub- or super-script attached? (e.g. N<sup>3-</sup>, S<sup>2-</sup>, K<sup>+</sup>, O<sub>2</sub>, or F<sub>2</sub>)
How about when a single letter elemental symbol is next to a sign of comparison in an equation? (e.g. 3 mol O = 3x16.00 g = 48.00 g O)
Nothing can be found with the reference material the shop has on hand.
Consensus in both cases is: “Yes, the letter sign would be required.” The reasoning is that the elemental symbols would be treated the same as abbreviations rather than variables in these cases. The letters cannot be replaced with numbers to solve the problem and the letter sign IS required for abbreviations in situations such as these.
Thank you for your question. Thank you especially for sharing your reasoning, which I believe is on the money.
I agree that you would follow rules for abbreviations in transcribing the single letter chemical symbols you mention (N for Nitrogen, N[superscript 3 minus] for the anion of Nitrogen that has three extra electrons, O for Oxygen, etc.) By this logic, yes, you would also need an English letter indicator for the O in "3 mol O = 3×16.00 g = 48.00 g O".
If I find a really good reference for this (or really good reference against this), I will post here again.