Connect atomic evidence, quantities and explanations
Use six original changed cases to test whether a conclusion survives a change in representation or assumption.
These public cases sample isotope evidence, composition, ion configurations, removal energies, periodic properties and valence reasoning. They do not establish complete Unit 1 coverage, AP readiness, independent mastery or practical laboratory technique.
Write reasoning before recording each response. First and latest answers, up to three attempts and known feedback exposure are retained in Science backups. Explanation drafts remain editable after feedback and are not automatically graded. An older import does not make an exposed case fresh. Keys are inspectable in this static application; these cases are not a secure exam.
0/6 attempted; 0/6 first responses match the keys. These counts award no course mastery and do not change existing completion requirements.
Reconstruct an isotope mixture
An original two-isotope detector packet has masses 20.0 u and 22.0 u, with signals 60 and 40. Assume equal detector response and singly charged ions. Find the weighted mean mass in u. Explain the normalization and whether doubling both signals changes your answer.
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0/3 attempts retained. No feedback exposure is recorded.
Separate ratio, molecular formula and structure
A pure compound has C:H:O mass ratio 12:2:16 and independently measured molar mass 90 g/mol. Use stipulated atomic molar masses C=12, H=1, O=16 g/mol. Which conclusion follows? Explain what remains unknown.
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0/3 attempts retained. No feedback exposure is recorded.
Combine proton count with a schematic spectrum
An ion has 13 protons and charge +3. A stipulated complete schematic spectrum shows occupied-subshell populations 2, 2, 6. Which interpretation is consistent? Explain why electron count alone does not identify the nucleus.
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0/3 attempts retained. No feedback exposure is recorded.
Infer a shell boundary without overidentifying an element
An original synthetic atom has successive removal energies 6, 12, 25 and 120 eV. Under the declared main-group shell-jump interpretation, three outer electrons precede a core removal. How much energy in eV is required to reach +3 from the neutral gas atom? Explain why the jump alone does not uniquely name the atom.
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0/3 attempts retained. No feedback exposure is recorded.
Resolve apparently conflicting periodic evidence
Selected F and Cl affinities are 3.401191 and 3.612709 eV. Their Pauling electronegativities are 3.98 and 3.16. Which statement is supported? Name the starting and ending species for attachment, and explain why the rankings differ without contradiction.
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0/3 attempts retained. No feedback exposure is recorded.
Transfer the charge and energy ledger
A synthetic group-2 metal M requires 8 and 16 eV for its first two removals. Each gas Cl atom releases 3.6 eV on attachment; the model stipulates 20 eV additional stabilization per formula unit. Which conclusion follows from neutral gas atoms? State the charge balance and explain what evidence would still be needed to predict a reaction rate.
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0/3 attempts retained. No feedback exposure is recorded.
Independent review still needs evidence
A reviewer should inspect units, normalization, particle identity, system boundaries and the distinction between a prediction and a measurement. Use a fresh case with different evidence and check reasoning separately from numerical agreement. Saved text and these public keys do not provide that independent review.
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