Nuclei Are Count Ledgers

Alpha Decay Removes Four and Two

Alpha emission changes both mass number and proton number. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Alpha decay removes four and two

The parent has A 20 and Z 10. The daughter has A 16 and Z 8.

20−4=1610−2=820-4=16\quad 10-2=8
Alpha decay ledgerAlpha changes both mass and proton counts.alphaparent A=20 Z=10 N=10daughter A=16 Z=8 N=8emit A=4 Z=2dE=0 J

The emitted alpha carries the missing counts

The emitted alpha ledger carries A 4 and Z 2 exactly.

α: A=4, Z=2\alpha:\ A=4,\ Z=2
Alpha emission sourceThe daughter and emitted ledgers close together.alphaparent A=20 Z=10 N=10daughter A=16 Z=8 N=8emit A=4 Z=2dE=0 J