Drupal 7: facebook comment for article only
In Drupal 7 you can use 


Facebook Comments Box : This module gives your site the ability of using Facebook's Comments Box social plugin. It will create a block just configure only for article. You can check this video
Facebook Comments Social Plugin : Implement Facebook commenting with settings on the level of both content type and node.
Using Facebook plugin code

&#60;div class="fb-comments" data-href="[CURRENT_ARTICLE_PAGE_URL]" data-numposts="5" data-colorscheme="light"&#62;&#60;/div&#62;
NOTE : 


YOUR_URL : Updated current URL based on each article.