The introduction for an academic paper is typically between 300 and 500 words; it may be longer depending on the journal and the topic, but it is recommended that it is as concise as possible.
The Introduction of a scientific paper has two objectives: (1) to stimulate the reader’s interest and, (2) to provide enough detail for the reader to fully understand why the study was conducted, what was the objective of the study, and how it was performed.
The Introduction must include all the information needed to follow the development of your findings. Avoid information that is not directly related to the research question, as it will only distract the reader.
The structure of the Introduction should be as follows: (1) what was KNOWN about the research problem, (2) what was NOT KNOWN, (3) what was the research question, (4) what was done to answer the question.
In the following Document you will find an example of this structure. You will read a very short introduction that, despite its conciseness (around 70 words), is complete and well structured.