Source: https://guthlabs.ai/docs/instruments/electronegativity-difference-bond-type-predictor/mechanism/

instrument mechanism / verified-clean

# Electronegativity Difference / Bond Type Predictor mechanism

The inspectable method record for Electronegativity Difference / Bond Type Predictor, kept separate from implementation and qualification.

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

## Model scope

The arithmetic and absolute-difference formula are valid, but the specification needs an explicit Pauling table/version, exact inclusivity at the 0.5 boundary, unsupported-element behavior, and stronger labeling that the bond-type result is only a heuristic. The unresolved table and boundary details make the specification NEEDS_REVIEW.

- The calculation ΔEN = |EN_A − EN_B| is correct when both values use the same Pauling electronegativity scale.

- The rule bands are a common rule of thumb, not a universal bond-type law; thresholds vary by reference and do not account for molecular context, oxidation state, resonance, or bond environment.

- The classification at exactly ΔEN = 0.5 is not explicitly stated as inclusive. The notation "0.5-1.7" suggests inclusion, but this should be specified; ΔEN = 1.7 is explicitly polar under the stated inequalities.

- Some real bonds such as H–F are commonly described as polar covalent despite exceeding the stated 1.7 ionic threshold, so the output should be labeled heuristic rather than definitive.

- The Pauling electronegativity lookup values and rounding precision are not specified, so reproducible results are ambiguous.

## Units and conventions

- Electronegativity is dimensionless on the Pauling scale; ΔEN is therefore dimensionless and has no physical unit.

- Both selected elements must use the same Pauling electronegativity table and the same numeric precision.

- Test vectors assume commonly tabulated Pauling values: H = 2.20, F = 3.98, C = 2.55, O = 3.44, Na = 0.93, and Cl = 3.16.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "element_A": "O",
    "element_B": "O",
    "EN_A_Pauling": 3.44,
    "EN_B_Pauling": 3.44
  },
  "expected_outputs": {
    "delta_EN": 0,
    "predicted_bond_type": "nonpolar covalent"
  },
  "working": "ΔEN = |3.44 − 3.44| = |0.00| = 0.00. Since 0.00 < 0.5, the rule predicts nonpolar covalent. This is the zero-difference edge case."
}
````

## Failure boundary

- Elements without a standard or agreed Pauling electronegativity value, including some noble gases and certain less-common elements, need an explicit unsupported-input behavior.

- A missing lookup value must not silently become zero or produce NaN; the instrument should return a clear unavailable-data error.

- The same element should normally produce ΔEN = 0 and nonpolar covalent under this rule, although actual bonding context can still matter.

- Rounded lookup values can move a result across a threshold, especially near ΔEN = 0.5 or 1.7.

- The lookup table version, values, and precision must be fixed and exposed for reproducibility.

- No division-by-zero hazard exists in the stated formula.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/electronegativity-difference-bond-type-predictor/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/electronegativity-difference-bond-type-predictor/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/electronegativity-difference-bond-type-predictor/qualification/>)

## 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`