Source: https://guthlabs.ai/docs/instruments/electronegativity-difference-bond-type-predictor/
instrument / verified-clean
# Electronegativity Difference / Bond Type Predictor
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]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Chemistry & Materials
**Tranche**: tranche-6
**Evidence ID**: t6-127
**Ledger rows**: 1
No ledger note is attached.
## Review findings
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.
### Formula and scope findings
- 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.
### Unit assumptions
- 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.
## Boundary hardening
### Recorded hazards
- 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.
## 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": {
"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."
}
````
## 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`