How many keywords are you trying to target? What is your keyword strategy?
You will need to do some research (or have someone do it for you) to figure this out and come up with a plan. There is no magical number of keywords per article. You want to use your keywords, but you also want your articles to be natural and written for the readers, not just for search engines. If you try too hard to include a keyword X number of times, it can make the article seems spammy and readers will lose interest.