Lewis Structure / Formal Charge Helper mechanism

Model scope

The formal-charge equation is standard, but the valence-electron equation and charge handling are materially incomplete. The honest-label warning about resonance and expanded octets is appropriate but should also mention radicals, incomplete-octet species, transition metals, and the need for explicit resonance/structure review.

• The total-valence-electron formula Σ(group number) is incorrect as written for main-group elements in groups 13–18: use valence-electron mapping 1, 2, 3, 4, 5, 6, 7, 8 for groups 1, 2, 13, 14, 15, 16, 17, 18, respectively. For example, oxygen contributes 6, not group number 16.
• The total-electron formula omits ionic charge. The correct expression is total valence electrons = sum of neutral-atom valence electrons − formal molecular charge, where a negative charge adds electrons.
• Formal charge FC = valence electrons − nonbonding electrons − ½(bonding electrons) is correct, provided bonding electrons means all bonding electrons incident on that atom.
• The octet-check algorithm is unspecified. It must define duet handling for hydrogen, octet handling for main-group atoms, and treatment of odd-electron species, incomplete octets, expanded octets, and hypervalent atoms.

Units and conventions

• Electron counts are dimensionless integer counts of electrons.
• Molecular charge is measured in elementary-charge units: +1 means one electron is removed and −1 means one electron is added.
• Bond order is dimensionless; a single, double, or triple bond contributes 2, 4, or 6 bonding electrons respectively.
• The vectors assume main-group elements and an explicitly supplied Lewis connectivity/lone-pair assignment.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "molecular_formula": "H2O",
    "charge": 0,
    "atoms": [
      {
        "id": "O1",
        "element": "O",
        "group": 16,
        "lone_pair_electrons": 4
      },
      {
        "id": "H1",
        "element": "H",
        "group": 1,
        "lone_pair_electrons": 0
      },
      {
        "id": "H2",
        "element": "H",
        "group": 1,
        "lone_pair_electrons": 0
      }
    ],
    "bonds": [
      {
        "between": [
          "O1",
          "H1"
        ],
        "order": 1
      },
      {
        "between": [
          "O1",
          "H2"
        ],
        "order": 1
      }
    ]
  },
  "expected_outputs": {
    "total_valence_electrons": 8,
    "formal_charge": {
      "O1": 0,
      "H1": 0,
      "H2": 0
    },
    "octet_check": {
      "O1": {
        "required_electrons": 8,
        "assigned_electrons": 8,
        "satisfied": true
      },
      "H1": {
        "required_electrons": 2,
        "assigned_electrons": 2,
        "satisfied": true
      },
      "H2": {
        "required_electrons": 2,
        "assigned_electrons": 2,
        "satisfied": true
      }
    }
  },
  "working": "Valence count: O=6 (group 16 maps to 6), H=1, H=1; neutral total = 6+1+1 = 8; charge adjustment = −0 = 0, so total = 8. O has 4 nonbonding electrons and 4 bonding electrons from two single bonds: FC(O)=6−4−(4/2)=0. Each H has 0 nonbonding electrons and 2 bonding electrons: FC(H)=1−0−(2/2)=0. Octet check: O has 4 nonbonding + 4 bonding = 8; each H has 2 bonding = 2."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

An out-of-domain element symbol produces undefined valence-electron and formal-charge results; the instrument should reject it rather than propagate undefined values.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche6/tranche6-results.json
• BOUNDARY_HAZARD_CATALOG.json