Problem 4
If a radioactive isotope of thorium (atomic number 90 , mass number 232) emits 6 alpha particles and 4 beta particles during the course of radioactive decay, what is the atomic number and mass number of the stable daughter product?
Problem 5
A hypothetical radioactive isotope has a half-life of 10,000 years. If the ratio of radioactive parent to stable daughter product is \(1: 3,\) how old is the rock containing the radioactive material?
Problem 6
Solve the problems below that relate to the magnitude of Earth history. To make calculations easier, round Earth's age to 5 billion years. a. What percentage of geologic time is represented by recorded history? (Assume 5000 years for the length of recorded history) b. Humanlike ancestors (hominids) have been around for roughly 5 million years. What percentage of geologic time is represented by the existence of these ancestors? c. The first abundant fossil evidence does not appear until the beginning of the Cambrian period, about 540 million years ago. What percentage of geologic time is represented by abundant fossil evidence?
