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Adding or Changing Atoms


After selecting an atom or bond tool from the palette, it can be added as the first entry for a new structure by clicking in the drawing region.  Atoms can also be added as separate items from an existing structure by using Shift-Click (holding the Shift key down while adding the object).  A selected atom can replace an existing atom in the structure by simply clicking on the atom to be replaced.  For example, to draw pyridine, one might first add a benzene ring, then select the N atom from the palette and click on a ring carbon to replace it with a nitrogen.  The valence will be adjusted automatically when atoms are replaced.  If exchanging an atom would cause a valence violation, a warning notice will appear briefly below the palette and the substitution will be aborted.  However, you can override this restriction if necessary by using Valence.

Note that ring carbons may be displayed either explicitly or implicitly depending on the state of 'Show All Atoms', but hetero atoms  are always displayed.  If you prefer not to display alkyl carbons by default then you can select the Explicit Carbons option in the Startup Options page under Preferences. 
 
For information on adding stable isotopes to a structure see the Isotopes topic