Chemistry students often switch between ACS and APA depending on the course. Both styles require consistent references, but the formatting rules differ in ways that are easy to mix up.
In-text citations
ACS uses numbered references in order of appearance —superscript numbers or numbers in parentheses. APA uses author–date format: (Smith, 2024).
If you paste APA in-text citations into a chemistry lab report that requires ACS, your instructor will notice immediately. Match the style specified in the assignment brief.
Reference list formatting
APA puts the publication year in parentheses after the author. ACS puts the year in bold within the journal citation string. ACS italicizes journal volume numbers; APA italicizes the journal title.
Author formatting also differs: ACS uses semicolons between authors and inverted names with initials; APA uses commas and an ampersand before the last author in the reference list.
Which should you use?
Use ACS for chemistry, biochemistry, and materials science courses unless told otherwise. Use APA for psychology, education, and many social-science assignments. When in doubt, ask your instructor or check the journal's author guidelines.