Check quantum numbers, solve reaction puzzles, and balance particle equations
Not every particle reaction can happen. A few strict bookkeeping rules decide which are allowed. Test them by building, judging, and balancing reactions.
Drag particles into the reactant and product zones, then check whether the reaction conserves all quantum numbers. See exactly which conservation laws are satisfied and which are violated.
Not every particle reaction is possible. Conservation laws act as gatekeepers: electric charge, baryon number, and lepton number must be conserved in every interaction. Additional quantum numbers (strangeness, charm, etc.) are conserved by the strong and electromagnetic forces but can change in weak interactions.
Test your understanding: for each reaction, decide whether it is allowed or forbidden by conservation laws. Can you identify which law is violated?
Click a column heading to sort the table. Use it as a cheat sheet for the puzzles on this page.
Every particle carries a unique set of quantum numbers. This table lists them all — use it as a reference when solving reaction puzzles.
Fill in the missing particle! Given an incomplete reaction equation, use conservation laws to determine what the missing particle must be.
Spot a mistake or have an idea?