STEM MODEL AND EVIDENCE WORKBENCH
Construct neutral ionic formula units from supplied charges and polyatomic flags, then audit verified and learner formulas.
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
Cross positive charge magnitudes into opposite ion counts and divide both counts by their greatest common divisor. Omit count one. Put parentheses around a supplied polyatomic fragment only when its reduced count exceeds one. The resulting positive and negative charge totals are equal by construction. A learner match means the exact reduced formula agrees with supplied ion evidence and fragment notation. A verified conflict points to the source row rather than silently grading against it. Ask learners to show charge totals, identify intact polyatomic ions, and explain why internal fragment subscripts do not change.
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 when ion identities and charge magnitudes are already verified and learners must construct the neutral formula unit. It does not infer charges, name compounds, choose oxidation states, validate ions or chemical existence, model lattices, or balance equations. It audits the answer key as well as the learner.
Calcium chloride and calcium nitrate match, including parentheses around two nitrate ions. Aluminum oxide is constructed as Al2O3, so AlO3 is flagged. Ammonium sulfate requires parentheses around repeated NH4; the learner string NH42SO4 is retained and marked for review.
Cross positive charge magnitudes into opposite ion counts and divide both counts by their greatest common divisor. Omit count one. Put parentheses around a supplied polyatomic fragment only when its reduced count exceeds one. The resulting positive and negative charge totals are equal by construction.
A learner match means the exact reduced formula agrees with supplied ion evidence and fragment notation. A verified conflict points to the source row rather than silently grading against it. Ask learners to show charge totals, identify intact polyatomic ions, and explain why internal fragment subscripts do not change.
Do not retain a common factor, write charges as formula subscripts, change a polyatomic ion internally, omit needed parentheses, put parentheses around a single ion, or use molecular prefixes. Confirm charge magnitudes and variable-charge metal states with an approved ion table before construction.
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
