1. * The graph below shows how the logarithm of the activity A of a radioactive isotope varies with time t. What is the half-life of the isotope? In (A/Bq) t/s 400 Choose one of the following answers. O 24 s O 55 s O 200 s O 0.42 s 2. A radioactive element X decays via electron emission with a half-life of 4 days to a stable nuclide of element Z. Which of the following statement is correct? Choose one of the following answers. O None of the other choices O After 8 days, the sample will consist of a quarter element Z and three-quarters of element X O Element Z will weigh EXACTLY as element X when the emission is complete O If element X has an atomic number of n, then element Z has an atomic number of n-1

1. * The graph below shows how the logarithm of the activity A of a radioactive isotope varies with time t. What is the half-life of the isotope? In (A/Bq) t/s 400 Choose one of the following answers. O 24 s O 55 s O 200 s O 0.42 s 2. A radioactive element X decays via electron emission with a half-life of 4 days to a stable nuclide of element Z. Which of the following statement is correct? Choose one of the following answers. O None of the other choices O After 8 days, the sample will consist of a quarter element Z and three-quarters of element X O Element Z will weigh EXACTLY as element X when the emission is complete O If element X has an atomic number of n, then element Z has an atomic number of n-1