NEET Sample Paper NEET Sample Test Paper-71

  • question_answer
    \[_{92}^{238}U\] has 92 protons and 238 nucleons. It decay by emitting an alpha particle and becomes

    A) \[_{92}^{234}U\]                    

    B) \[_{90}^{234}Th\]

    C) \[_{92}^{235}U\]                    

    D) \[_{93}^{237}Np\]

    Correct Answer: B

    Solution :

    As a general rule in any decay sum of mass number A and atomic number Z must be the same on both sides. Let the daughter nucleus be \[_{Z}^{A}X\]. So, reaction can be shown as \[_{92}^{238}U\,\xrightarrow{{}}\,_{Z}^{A}X\,\,+\,\,_{2}^{4}He\] From conservation of atomic mass \[238=A+4\] \[\Rightarrow \,\,\,\,\,\operatorname{A} =234\] From conservation of atomic number \[92=Z+2\] \[\Rightarrow \,\,\,\,\,\,\,Z=90\] So, the resultant nucleus is \[_{90}^{234}X\], i.e., \[_{90}^{234}Th\].


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