Three reaction rows show why charge, baryon number, and lepton families must all close. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Muon decay closes both family ledgers
The accepted muon row keeps scaled charge -3, electron-family total 0, and muon-family total 1 on both sides.
−301⇒1
Electron to photons fails lepton number
The electron row starts with scaled charge -3 and electron-family number 1, while two photons total 0 and 0.
−3=01=0
Proton decay closes charge but not baryon number
The proton row keeps scaled charge 3 on both sides, but scaled baryon number changes from 3 to 0.