Isotope / Average Atomic Mass Calculator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t5-025

Effect

Computation or source lookup only

Input and validation requirements

• Reject negative abundances.
• Validate that abundances sum to 100% when percentage inputs are used, or 1.0 when fractional inputs are used; otherwise the result is not a valid weighted average.
• If an implementation normalizes abundances by their sum, an all-zero abundance list causes division by zero.
• Require isotope masses and abundances arrays to have equal nonzero length.
• Do not silently mix percentage and fractional abundance representations.
• Built-in isotope data must identify its NIST/IUPAC source, reference composition, and revision because natural isotope abundances can be reference-dependent.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "isotope_masses_u": [
      34.96885,
      36.9659
    ],
    "abundances_percent": [
      75.78,
      24.22
    ]
  },
  "expected_outputs": {
    "average_atomic_mass_u": 35.45253551
  },
  "working": "Convert percentages: 75.78%=0.7578 and 24.22%=0.2422. Compute 34.96885×0.7578=26.49939453. Compute 36.96590×0.2422=8.95314098. Add: 26.49939453+8.95314098=35.45253551 u."
}

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-tranche5/tranche5-results.json