code: private static boolean familyHalogen(IAtom atom) {
          String symbol = atom.getSymbol();
          if (symbol.equals("F") || symbol.equals("Cl") || symbol.equals("Br") || symbol.equals("I"))
              return true;
          else
              return false;
      }
docs: Looking if the IAtom belongs to the halogen family.
  The IAtoms are F, Cl, Br, I.
  
  @param  atom  The IAtom
  @return       True, if it belongs