Okay, so it's not snake-related, but it's cute and related to science! And it comes with this lovely guide on how to draw your own atoms!
Pretty easy, isn't it! Your circles don't have to be blue or black, but those colors are what I prefer for my atoms. This can be done in almost any paint program, as long as it has a selection of colors, an Ellipse tool, and a Text tool, which are pretty standard.