1   x  11   c3              Tetravalent carbon                                                              OK  conn 
2   x  12   ce cf c2 cc cd  Trivalent carbon, double bonded to carbon                                       OK  conn 
3   x  13   ce cf c2 cc cd  Trivalent carbon, double bonded to nitrogen or phosphorus                       OK  conn
4   x  14   c ce cf c2 cc cd  Trivalent carbon, double bonded to oxygen or sulfur                             OK  conn  
5   x  15   c1              Univalent or divalent carbon                                                    OK  ring + conn 
6   x  16   ca              Aromatic carbon                                                                 OK  ring + conn
7   x  17   ca              Aromatic carbon bonded to an aromatic oxygen or nitrogen with a lone pair       OK  ring + conn
8   x  21   nh              Amine nitrogen                                                                  OK  conn + angle
9   x  22   nc nd  n3  na   Trivalent nitrogen with a delocalized lone pair                                 OK (dihydropyrrole) in ring
10     23   nb   n          Trivalent nitrogen with a highly delocalized lone pair                          OK pyrrole
11     24   n2              Neutral divalent nitrogen                                                       OK -N=N
12     25   n1              Univalent or cationic divalent nitrogen                                         OK -N=N+ 
13     31   os oh           Univalent or divalent oxygen                                                    OK  conn
14     32   o               Double-bonded oxygen in an ester or acid                                        OK  conn 
15     33   o (b to ring)   Double-bonded oxygen in a lactone or lactam                                     OK  conn ring 
16     41   p2 p3           Divalent or trivalent phosphorus                                                OK  conn
17  x  42   p4 p5           Trivalent or tetravalent double-bonded phosphorus                               OK  conn
18     51   ss sh s2        Univalent or divalent sulfur                                                    OK  conn
19     52   s4              Trivalent sulfur                                                                OK  conn
20     53   s6              Tetravalent sulfur                                                              OK  conn 
21  x  61   Si              Tetravalent silicon                                                             OK  atom
22     71   f               Fluorine                                                                        OK  atom 
23     72   cl              Chlorine                                                                        OK  atom
24     73   br              Bromine                                                                         OK  atom
25     74   i               Iodine									     	 OK  atom 
26     91   h*              Hydrogen								     	 OK  atom

 1     01   Single bond  								 OK  atom conn
 2     02   Double bond								     	 OK  atom conn
 3     03   Triple bond								     	 OK  atom conn
 4     06   Dative bond								     	 OK  atom conn 
 5     07   Aromatic single bond							     	 OK  atom conn ring
 6     08   Aromatic double bond							     	 OK  atom conn ring 
 7     09   Single bond with charge or delocalized bond                                       
