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The positron is antiparticle of

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Important Questions on Atomic Structure and Particle Physics

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The particles not emitted by radioactive substance are
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A plot of the number of neutrons (N) against the number of protons (P) of the stable nuclei exhibits upwards deviation from linearity for atomic number, Z>20 . For an unstable nucleus having N P ratio less than 1, the possible mode(s) of decay is (are):
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Originally the radioactive beta decay was thought as a decay of a nucleus with the emission of electrons only (Case I) . However, in addition to the electron, another (nearly) massless and electrically neutral particle is also emitted (Case II). Based on the figure below, which of the following is correct?

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A nucleus of uranium decays at rest into nuclei of thorium and helium. Then:
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The atomic number and the mass number of an atom remains unchanged when it emits
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In a radioactive decay chain, the initial nucleus is  90232Th. At the end, there are 6 α-particles and 4β-particles which are emitted. If the end nucleus is ZAX, A and Z are given by:
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A sample of 210Po which is α - emitter with T12=138  days is observed by a student to have 2000 disintegrations (2000 Bq). What is the mass of the 210Po sample ?

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Atomic weight of Th is 232 and its atomic number is 90. The number of α - and β - partilces which will be lost so that an isotope of lead (atomic weight 208 and atomic number 82) is produced is
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90Th228 emits four alpha and one beta particles. Number of neutrons in daughter element is:
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The 'rad' is the correct unit used to report the measurement of
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Which of the following isotopes is used for treatment for cancer?
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How many α-particles are emitted in the nuclear transformation :

8 4 Po 2 1 5 8 2 Pb 2 1 1 + 2 He 4
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The probability of survival of a radioactive nucleus for one mean life is:

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In which of the following decays the atomic number decreases?

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How many α - particles will be emitted when 90Th234 changes into 84Po218 ?
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 90Th234 disintegrates to give  82Pb206 as the final product. How many α and β- particles are emitted out during this process?
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 92U235 undergoes successive disintegrations with the end product of  82Pb203. The number of α anβ- particles emitted are