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⁴²K
Potassium-42
Radioisotope ⁴²K. Mass number A = 42. β⁻ parent of stable ⁴²Ca.
Potassium-42 (Z = 19, A = 42) is a β⁻ radioisotope that decays to stable ⁴²Ca. The MIRD monograph prints a half-life of about 12.36 h. NNDC prints 12.355 h. It was used as a tracer for potassium exchange.
What it supports
An exact A = 42 medical radioisotope whose daughter is the calcium-42 neighbor. The decay tables are the hard number. The two half-lives stay side by side. They are not averaged.
What it does not
Not a current first-line clinical protocol. Not molybdenum. Not argon-42. Not one exact made by collapsing MIRD 12.36 h and NNDC 12.355 h. Many radioisotopes have A = 42. The strength is documented tracer use and the decay to calcium-42.
ExactnessExact
Form42
UnitA
Strengthhard
Hung24 September 2026