Electronegativity Difference / Bond Type Predictor mechanism

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

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