Practice mode / Nuclear Physics Isotopes of an element have ____ A Option A: the same number of neutrons but different numbers of protons B Option B: the same mass number but different atomic numbers C Option C: different numbers of protons and electrons D Option D: the same number of protons but different numbers of neutrons Correct answer D. the same number of protons but different numbers of neutrons Explanation Isotopes have the same atomic number Z, so they are the same element with the same chemistry, but different neutron numbers and hence different mass numbers. Show answer Report a problem Answer checked 11 October 2026 · How we write and check questions
Question 01 / Nuclear Physics What fraction of a radioactive sample remains undecayed after three half-lives? A Option A: 1/3 B Option B: 1/6 C Option C: 1/8 D Option D: 1/9 Correct answer C. 1/8 Show answer Open question
Question 02 / Nuclear Physics The activity of a source falls from 800 Bq to 100 Bq. If its half-life is 6 hours, how long did this take? A Option A: 24 hours B Option B: 48 hours C Option C: 18 hours D Option D: 8 hours Correct answer C. 18 hours Show answer Open question
Question 03 / Nuclear Physics A radioisotope has a decay constant of 0.0231 per day. What is its half-life (T½ = 0.693/λ)? A Option A: 16 days B Option B: 3.0 days C Option C: 43 days D Option D: 30 days Correct answer D. 30 days Show answer Open question
Question 04 / Nuclear Physics A 64 g sample of a radioisotope has a half-life of 2 hours. What mass of the isotope remains undecayed after 8 hours? A Option A: 8 g B Option B: 16 g C Option C: 4 g D Option D: 32 g Correct answer C. 4 g Show answer Open question
Discussion