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KVPY Sample Paper KVPY Stream-SX Model Paper-1

  • question_answer
    An element X decays, first by positron emission and then two \[\alpha \]-particles are emitted in successive radioactive decay. If the product nuclei has a mass number 229 and atomic, number 89, the mass number and atomic number of element X are

    A) 237, 93            

    B) 237, 94

    C) 221, 84            

    D) 237, 92

    Correct Answer: B

    Solution :

    \[_{z}{{X}^{A}}{{\to }_{z-1}}\underset{2\alpha +{}_{z-5}X{{'}^{A-B}}}{\mathop{\underset{\downarrow }{\mathop{{{Y}^{A}}}}\,}}\,+{{e}^{+}}+v\] Given \[A-8=224\] &          \[Z-5=89\]\[\Rightarrow \] \[A=237,\] \[Z=94.\]


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