code: @Override
      public boolean matches(IAtom atom) {
          String symbol = atom.getSymbol();
          int group = PeriodicTable.getGroup(symbol);
          return group == this.groupNumber;
      }
docs: /*
  (non-Javadoc)
  @see
  org.openscience.cdk.isomorphism.matchers.smarts.SMARTSAtom#matches(org
  .openscience.cdk.interfaces.IAtom)