There are a number of different styles or formats for citations, including MLA, APA and Turabian. Which style you use depends upon the subject discipline you are working in. For Chemistry you may use the ACS Style Guide. If you are uncertain about which style to use, ask your professor.
Use the pull-down menu under ACS Guide for Quick ACS Reference formatting or go to any of these sites for ACS citation help:
Citations identify published information in order to locate that item again. Citations of articles often include the author, title, magazine or journal name, page numbers and publication information. Citations of Web documents also include a URL and the day the information was accessed.
The list of the sources you used when researching your paper is called a bibliography or works cited page. These sources are listed in citation format and follow an established style, such as MLA (Modern Language Association), APA (American Psychological Association) or Chicago Manual of Style. The bibliography allows others who read your work to verify facts or research the same information more easily.