Hi Gavin,
maybe you have solved your problem yet.
\startformula
{\null}^^{194}__{38}{\rm Sr}
or {\hbox{Xe}}^^{140}__{54}.
\stopformula
Better, ConTeXt way could be the variation on \chem:
\unexpanded\def\isotope#1#2#3{\dontleavehmode\begingroup\null\lohi[left]{#2}{#3}#1\endgroup}
\isotope{Sr}{38}{194}
or (with more logical order of parameters)
\unexpanded\def\isotope#1#2#3{\dontleavehmode\begingroup\null\lohi[left]{#1}{#2}#3\endgroup}
\isotope{38}{999}{Sr}
Or for text and math modes together:
\unexpanded\def\isotope#1#2#3{%
\ifmmode\begingroup\null^^{#1}__{#2}{\rm#3}\endgroup%
\else\dontleavehmode\begingroup\null\lohi[left]{\tfx #1}{\tfx#2}\rm#3\endgroup%
\fi}
\isotope{999}{38}{Sr}
\startformula
\isotope{999}{38}{Sr}
\stopformula
You can do it either way, whichever way suits you better.
Tomáš
________________________________
Od: ntg-context
On 15 Apr 2023, at 19:19, Gavin via ntg-context
wrote: I’m writing nuclear reactions. When add prescripts to atomic symbols with two letters, (Be, Sr, Xe, etc.) the prescripts split the atoms!
One can use Unicode superscript and subscript numbers, as in ²³⁵₉₂U, which is easier to read. For input, an editor supporting text substitutions might be used. ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / https://www.ntg.nl/mailman/listinfo/ntg-context webpage : https://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : https://contextgarden.net ___________________________________________________________________________________