These things are specified in the IUPAC nomenclature: https://iupac.org/what-we-do/books/bluebook/

Generally speaking, everything that regards the stereochemistry of a molecule is italicised.

Dear David Neil interesting question. In my personal experience both the capital N and the p with stands for para should be italic, so that N-acetyl-p-benzoquinoneimine is the cireect version. For more information please see this useful link entitled "On the use of italic and roman fonts for symbols in scientific text"

https://iupac.org/wp-content/uploads/2016/01/ICTNS-On-the-use-of-italic-and-roman-fonts-for-symbols-in-scientific-text.pdf

Dear David.

For many chemical branches there is the idea to mark so-called locants and some topological terms by the use of the italic font. This affects the organic chemistry (2H-prazole, Benzo[a]pyren .....), kappa nomenclature for complexes (k2N:N'), topological indicators like catena-poly[....] . Additionally all words from a foreign languages (via, per se ...) should be italic. But the attached number(s) should be given in a uprightt font.

If you keep these small hints in mind you will make some editors of chemical journals very happy. It is annoying to correct these issues in a chemical text.

For the inorganic questions I recommend:

https://iupac.org/wp-content/uploads/2016/07/Red_Book_2005.pdf

Best regards

Guido