What is the half-life of potassium-40 in years?

The half-life of potassium-40 that decays through beta emission is 1.28 × 109 years, however the half-life of potassium-40 that decays through positron emission is 1.19 × 1010 years.

How long will it take for potassium-40 to reduce by 50%?

Half-life (t½) is the amount of time required for a quantity to fall to half its value as measured at the beginning of the time period. After 1300 million years ( first half life) 200 /2 = 100 g decays and 100 g remains left.

Is Argon 40 Stable?

Argon (Ar) has three natural isotopes with masses 36, 38, and 40. Ar and 38Ar are stable, that is, they are not radioactive, and they are also not produced by radioactivity processes.