Title Unit No. 10 Radioactivity (S.C).pdf ✅

RADIOACTIVITY (UNIT-10) MDCAT Exam Notes | 1 www.isl.school Q1. The nucleus of one of the isotopes of nickel is represented by Ni 28 60 . Which line in the table correctly describes a neutral atom of this isotope? number of protons number of neutrons number of orbital electrons A 28 32 28 B 28 60 28 C 60 28 28 D 60 32 32 Q2. The following represents a sequence of radioactive decays involving two a-particles and one β -particle. At 85 217 α → V α → W β → X What is the nuclide X? (A) At 85 213 (B) 77Ir 215 (C) 82Pb 209 (D) Tl 81 217 Q3. Radon 86Rn 222 decays by a- and β-emission to bismuth Bi 83 214 . For the decay of each nucleus of radon, how many α- and β -particles are emitted? α-particles β -particles A 1 1 B 2 1 C 1 2 D 2 2 Q4. The symbol 32Ge 77 represents a nuclide of germanium that decays to a nuclide of arsenic (As) by emitting a β-particle. What is the symbol of this arsenic nuclide? (A) 32As 76 (B) 32As 78 (C) 31As 78 (D) 33As 77 Q5. A 92U 238 nucleus decays in two stages to a 91Pa 234 nucleus. What was emitted in these two stages? (A) α + β (B) α + γ (C) β + β (D) β + γ
RADIOACTIVITY (UNIT-10) MDCAT Exam Notes | 2 www.isl.school Q6. A different nucleus can be formed by bombarding a stable nucleus with an energetic α- particle. 11Na 23 is bombarded with an energetic α-particle. What could be the products of this nuclear reaction? (A) 10Ne + neutron 25 (B) 11Na + proton 25 (C) 12Mg + β 26 (D) 13Al + γ 27 Q7. A slow-moving neutron collides with a nucleus of uranium-235. This results in a nuclear reaction that is represented by the following nuclear equation 92U 235 + 0n 1 → 60Nd 154 + 32Ge 80 + x where x represents one or more particles. What does x represent? (A) one neutron (B) two electrons (C) two neutrons (D) two protons Q8. The diagram shows a sequence of radioactive decays involving three α-particles and a β − particle. 93Np 237 α → Q β − → R α → S α → T What is nuclide T? (A) 88Ra 235 (B) 88Ra 231 (C) 90Th 235 (D) 90Th 239 Q9. A nucleus of francium-221 ( 87Fr 221 ) decays into a nucleus of bismuth-209 ( Bi 83 209 ) in several steps. Which particles could be emitted? (A) 2 α -particles and 4 β − particles (B) 2 α -particles and 4 β + particles (C) 3 α -particles and 2 β −particles (D) 3 α -particles and 2 β + particles Q10. What is the correct equation for β + decay? (A) neutron → proton + electron + electron antineutrino (B) neutron. → proton + electron + electron neutrino (C) proton → neutron + positron + electron antineutrino (D) proton → neutron + positron + electron neutrino Q11. Activity is proportional to number of A) daughter nuclei C) decayed nuclei B) undecayed nuclei D) father nuclei Q12. The half-life of 234Th90 is 24 days. If 8 kilogram of this isotope is present initially, what amount remains after 72 days? A) 2 kg B) 1 kg C) 5 kg D) 4 kg

RADIOACTIVITY (UNIT-10) MDCAT Exam Notes | 4 www.isl.school Q22. Atomic mass number of an element thorium is 232 and its atomic number is 90. The end product of this radioactive element is an isotope of lead (atomic mass 208 and atomic number 82). The number of alpha and beta particles emitted is A) α=3, β=3 B) α=6, β=4 C) α=6, β=0 D) α=4, β=6 Q23. The half-life of polonium is 140 days. After how many days, 16 gm polonium will be reduced to 1 gm (or 15g will decay) A) 700 days B) 280 days C) 560 days D) 420 days Q24. What is the respective number of α and β particles emitted in the following radioactive decay 90X200→80Y168 A) 6 and 8 B) 8 and 8 C) 6 and 6 D) 8 and 6 Q25. In the disintegration series 92238U α → X β− → ZY A the values of Z and A respectively will be A) 92, 236 B) 88, 230 C) 90, 234 D) 91, 234 Q26. The half-life of radon is 3.8 days. Three forth of a radon sample decay in A) 5.02 days B) 15.2 days C) 7.6 days D) 11.4 days Q27. In beta decay A) The parent and daughter nuclei have same number of protons B) The daughter nucleus has one proton less than the parent nucleus C) The daughter nucleus has one proton more than the parent nucleus D) The daughter nucleus has one neutron more than the parent nucleus Q28. A radioactive substance has a half-life of 1 year. The fraction of this material, that would remain after 5 years will be A) 1/32 B) 1/5 C) 1/2 D) 4/5 Q29. A radioactive nucleus emits a beta particle. The parent and daughter nuclei are A) Isotopes B) Isotones C) Isomers D) Isobars Q30. In Fig. X represents time and Y represent activity of a radioactive sample. Then the activity of sample, varies with time according to the curve A) A B) B C) C D) D