Question
(a) Table 12.1 describes four nuclides.
(i) State which two nuclides have the same number of protons.
……………………………………………………………………………………………………………………. [1]
(ii) State which two nuclides have the same number of nucleons.
……………………………………………………………………………………………………………………. [1]
(iii) State which one of the four nuclides has the most electrons orbiting when it is in a neutral atom.
……………………………………………………………………………………………………………………. [1]
(b) Thorium-234 has a half-life of 24 days. A sample of radioactive material contains 40 mg of thorium-234.
Calculate the mass of thorium-234 remaining after 72 days.
mass of thorium-234 remaining = …………………………………………… mg [3][Total: 6]
Answer/Explanation
Ans: (a)(i) uranium-235 AND uranium-238
(a)(ii) plutonium(-238) AND uranium-238
(a)(iii) plutonium(-238)
(b) idea of 3 half-lives OR 72 ÷ 24 40 ÷ 8 5(.0) (mg)