В общем, Вы правильно понимаете.
scholar к химикам не применяется.
"Scientist" is used when referring specifically to a person who is an expert in a science, especially physical or natural sciences.
"Scholar" is more broad, and can be used generally for anyone who has profound knowledge of a particular subject.
"Scholar" isn't used for sciences (chemistry, geography), but can be used for History, Language, etc. Examples of this are: ...
http://english.stackexchange.com/questions/37111/scholar-vs-scientist Thus, "scholar" is only used for someone who is an expert at a particular subject, when the subject is not a science.