As years pass by search engine is no longer focus on the number of words in article. What they consider is the content of it and the related keywords on it that people are looking for in a website. The quality is more important over the quantity. People are visiting the pages and google is more focused on the time people are spending in your website and that increases the ranking on search engine results pages.
Number of Words
Quality content is consist of related words in your page with at least 250 to 300 word suggested word count. In writing article people sometimes think of the keywords to be used which are good on search engine.
Keyword frequency is also known as keyword density. It is the number of times keywords are being used in the article. As Google changes, search engine is not focus anymore on the amount of keywords used or how frequent they appeared in your content. The important now is how your keywords are being used in your content as the information of what you want to tell your readers. ]Keyword density is important in SEO because it helps relevant keywords analyzes its rate and check the weight of the content. Ideal density rate is changing as google changes its algorithms. So the best you can do is to use the proper keywords depending on your article needs, not thinking of SEO, just let new articles posted and search engine will do its job.