Source: https://guthlabs.ai/docs/instruments/lewis-structure-formal-charge-helper/

instrument / verified-clean

# Lewis Structure / Formal Charge Helper

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/lewis-structure-formal-charge-helper/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/lewis-structure-formal-charge-helper/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/lewis-structure-formal-charge-helper/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/lewis-structure-formal-charge-helper/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Chemistry & Materials

**Tranche**: tranche-6

**Evidence ID**: t6-131

**Ledger rows**: 1

No ledger note is attached.

## Review findings

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.

### Formula and scope findings

- 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.

### Unit assumptions

- 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.

## Boundary hardening

**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.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "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."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

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

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche6/tranche6-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`