Practically, there is no ideal word limit for an article... To engage your audience in a best way, try to provide the necessary information in the very first paragraph of the article... This paragraph should be trailer of your article. Make sure, what you are writing is informative and well written.
Length of article is not the matter, what matter is content of article. Ideally an article must be more than 250 words, rest depend on you how long article you want to write.