Mass number and proton count jointly set neutron count. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Fourteen and six leave eight neutrons

Mass number 14 minus proton count 6 leaves neutron count 8.

N=AZ=146=8N=A-Z=14 - 6=8
Isotope identity scanA, Z, and N labels are checked by the isotope ledger.A=14Z=6N=8

Twelve and five leave seven neutrons

Mass number 12 minus proton count 5 leaves neutron count 7.

N=AZ=125=7N=A-Z=12 - 5=7
Isotope identity scanA, Z, and N labels are checked by the isotope ledger.A=12Z=5N=7

Sixteen and eight leave eight neutrons

Mass number 16 minus proton count 8 leaves neutron count 8.

N=AZ=168=8N=A-Z=16 - 8=8
Isotope identity scanA, Z, and N labels are checked by the isotope ledger.A=16Z=8N=8