STEM MODEL AND EVIDENCE WORKBENCH
Audit electron accounting and formal-charge sums from explicit bond-order and lone-electron evidence for proposed structures.
Review output
Load the worked example to inspect realistic inputs, or enter anonymous classroom or laboratory evidence. Results remain in this browser tab until you copy or download them.
Transparent method
Accounted electrons equal two times the sum of all bond orders plus the count of individual lone electrons. Electron accounting passes when that equals the supplied expected valence pool. Charge accounting passes when the supplied sum of atom formal charges equals the expected overall species charge. Completeness requires both. A supported claim agrees with both totals. A conflict locates electron accounting, charge accounting, or both, but cannot prove which atom or bond is wrong. Return to atom-by-atom valence contributions and formal charge, then review octets, exceptions, resonance, connectivity, and geometry separately.
Confirm the task, approved source, units, notation, signs, model assumptions, and review threshold. Keep an unchanged copy of measurements or learner responses.
Run the worked example, inspect every intermediate row, and compare the result with a hand calculation, diagram, physical model, periodic table, or approved laboratory method.
Record the method, assumptions, uncertainty, units, classifications, and flagged rows. Verify the editable report independently before instruction, assessment, or laboratory use.
How to interpret the result
Use after a learner draws a Lewis candidate and needs separate electron-pool and charge-sum checks. It does not infer connectivity, draw bonds, assign lone pairs, calculate individual formal charges, test octets, choose resonance contributors, predict geometry, or establish chemical stability. Those remain visible follow-up reviews.
Water, carbon dioxide, and ammonium account for the expected electron pools and charges. The nitrate candidate accounts for twenty-four electrons but its supplied formal-charge sum is zero instead of negative one, so a yes claim is flagged. An incomplete oxygen candidate has ten of twelve electrons and is correctly claimed incomplete.
Accounted electrons equal two times the sum of all bond orders plus the count of individual lone electrons. Electron accounting passes when that equals the supplied expected valence pool. Charge accounting passes when the supplied sum of atom formal charges equals the expected overall species charge. Completeness requires both.
A supported claim agrees with both totals. A conflict locates electron accounting, charge accounting, or both, but cannot prove which atom or bond is wrong. Return to atom-by-atom valence contributions and formal charge, then review octets, exceptions, resonance, connectivity, and geometry separately.
Do not count lone pairs as one electron, forget that each bond order contributes two electrons, omit ionic charge adjustment, confuse oxidation state with formal charge, or treat correct totals as proof of a valid structure. Check radicals, expanded octets, resonance, and course conventions explicitly.
Learning boundary
This browser-local workbench applies only the disclosed rules. It cannot diagnose learning, certify an experiment, identify a substance, establish a structure, or replace teacher, laboratory, and safety judgment.
Review checklist
Practical questions
No. Processing occurs in the current browser tab. Avoid personal information and retain authoritative records only in the school-approved system.
No. It describes entered evidence under one disclosed rule. Compare several evidence sources and ask for reasoning before drawing a conclusion.
Treat it as an editable calculation aid. Show your own reasoning, cite required sources, and follow the course method and academic-integrity rules.
YOUR NIRMION
