# Radioaktivität
## A1:
### Potassium-Argon Dating
Potassium-Argon dating is a technique used to determine the age of rocks and minerals based on the decay of potassium-40 (K-40) to argon-40 (Ar-40).
**a)** A rock sample contains 1 gram of potassium-40 and 9 grams of argon-40. Calculate the age of the rock sample. The half-life of K-40 is 1.3 billion years.
**b)** A mineral sample contains 33 grams of potassium-40 and 90 grams of argon-40. Determine the age of the mineral sample.
**c)** What type of decay is this, write the formula
**d)** Assuming the potassium is found in the Form of KCl, what combinations, and in which ratio of isotope mixtures would you expect?
$K = 93.26\% ^{39}K + 0.01\% ^{40}K + 6.73\% ^{41}K$
$Cl = 75.77\% ^{35}Cl + 24.23\% ^{36}Cl$
### Uranium-Lead Dating
Uranium-Lead dating is a radiometric dating technique used to determine the age of rocks and minerals. The decay of uranium-238 (U-238) to lead-206 (Pb-206) is utilized in this method.
**a)** A rock sample initially contains 100 grams of uranium-238 and 400 grams of lead-206. Determine the age of the rock sample. The half-life of U-238 is 4.5 billion years. The rock now contains 420 grams of lead.
**b)** A mineral sample initially contains 20 grams of uranium-238 and 80 grams of lead-206. Calculate the age of the mineral sample. The rock now contains 81 gramms of lead
**c)** Find a plausible decay series using your isotope chart, and compare with you neighbour