Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             reactive intermediates
               1 Class radicals [X•]
               2 Class diradicals [X:, X•Y•]
               3 Class radical ions
               4 Class cations [X+]
               5 Class anions [X‾]
               6 Class dipolar compounds