Default:HF, HCl, HBr, HI, HAt

Molecules:

• Neutral atoms: 1 bond is allowed.
  Exceptions:

  • 3 valence:

    • Two of the ligands should be F, Cl or oxygen; and one more atom from the 14th, 15th, 16th columns.

    • Double bonded oxygen and one any other atom from 14th, 15th, 16th columns are also accepted.

  • 5 valence:

    • Four of the ligands should be F, Cl or oxygen; and one more atom from the 14th, 15th, 16th columns. Double bonded oxygens are accepted.

  • 7 valence:

    • IF₇ is accepted.

  • Halogen oxoacids:

    • HXO_y, where X = Cl, Br, I or At; and y = 2, 3 or 4.

Ions:

• F^-, Cl^-, Br^-, I^-, At^- are accepted.

• 1+ charged ions: 2 filled valences are necessary (bonds or radicals). If absent, implicit Hydrogen atoms added.

Radicals:

• 1 Radical with 0 bond around the halogen atom is accepted.