The isotope 238 U decays to 206Pb with a half-life of 4.47 x 10° y. (Although the decay occurs in many individual steps, the first step has by far the longest half-life, so the decay can be considered to go straight to lead.) A rock recovered far underground is found to contain 0.76 mg of 238 U, 0.17 mg of 206pb, and 1.4 mg of 40 Ar. Assume that 40K decays to only 40 Ar with a half-life of 1.25 x 10 y. How much 40K will it likely contain? me

The isotope 238 U decays to 206Pb with a half-life of 4.47 x 10° y. (Although the decay occurs in many individual steps, the first step has by far the longest half-life, so the decay can be considered to go straight to lead.) A rock recovered far underground is found to contain 0.76 mg of 238 U, 0.17 mg of 206pb, and 1.4 mg of 40 Ar. Assume that 40K decays to only 40 Ar with a half-life of 1.25 x 10 y. How much 40K will it likely contain? me