Skeletal formula challenge
Type a molecular formula. Press Enter to check.
Guided explains how to get the answer. Your choice is saved across the organic games in this browser.
Time attack advances quickly. Use Review answers afterwards. Opening an explanation stops automatic progression; the clock keeps running.
Give the molecular formula.
Loading structure…
Ordinary numbers are fine. No subscripts needed.
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Your previous answers
Up to 60 recent answers are kept in this browser when storage is available. They are separate from your My Chemistry round scores and will not appear on another device.
How to play
Shown structure: count the atoms in the drawing. Hidden structure: use the description to work out the molecular formula. Type ordinary letters and numbers. Press Enter to check, then Enter for the next question.
Hidden structure has no picture or compound name to reveal. Its clues determine a molecular formula; different structures may fit. Starter uses rings, C=C bonds, alcohols and halogens. Later levels add carbonyls, nitrogen and aromatic rings. Stretch includes group ratios and hydrogen-uptake data. Guided feedback opens after an incorrect answer in untimed practice. In Time attack, you can review the explanations after the round.
Practice has no time limit. Quick 10 finishes after ten answers. In Time attack, the clock starts when the first question is ready and keeps running between questions and when you switch tabs. An incorrect answer scores zero. Streak tracks your longest run of correct answers.
Display to class adds a timer, size controls and Reveal answer. Classroom and teacher previews stay out of personal results.
My recent rounds
Formula challenge 0.3.0