Potassium-argon dating, method of determining the time of origin of rocks by measuring the ratio of radioactive argon to radioactive potassium in the rock. This dating method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40.

What is the half life of potassium-argon dating?

about 1,300 million years The Potassium-Argon dating method is the measurement of the accumulation of Argon in a mineral. It is based on the occurrence of a small fixed amount of the radioisotope 40K in natural potassium that decays to the stable Argon isotope 40Ar with a half-life of about 1,300 million years.

Why is U 235 better than U-238?

U- 235 is a fissile isotope, meaning that it can split into smaller molecules when a lower-energy neutron is fired at it. U- 238 has an even mass, and odd nuclei are more fissile because the extra neutron adds energy - more than what is required to fission the resulting nucleus.