ChEMBL

There was a post a few weeks ago about elemental compositions - simple cases of Carbon oxides, nitrogen oxides, etc. Well, I've processed ChEMBL to do the analysis across all of the compounds - very simple analysis - select all formulas of all compounds, select only those that are contain only elements restricted to the set CHNO, and then plot the heavy element (i.e. C N or O) fractions on a ternary plot.

Here it is (click image for larger).
So, the compounds that chemists make are mostly carbon-based, and of course, there's no contours on this version of the plot - hardly a big surprise, that's why they are organic, but things get more interesting when you think about using these data as filters/heuristics for expectation values for the sort of things that chemists could make, for spotting unusual compounds, etc. etc. More later on this...

Update: Here is the plot for drugs. As you will see there are some differences...