BHU PMT BHU PMT (Screening) Solved Paper-2005

  • question_answer
    In the reaction given below \[_{86}{{A}^{222}}{{\xrightarrow{{}}}_{84}}{{B}^{210}}\]how many a and p-particles are emitted?

    A)  \[6\alpha ,3\beta \]                                      

    B)  \[3\alpha ,4\beta \]

    C)   \[4\alpha ,3\beta \]                                     

    D)  \[3\alpha ,6\beta \]

    Correct Answer: B

    Solution :

                     Key Idea: \[\alpha -\]particle is the helium nucleus\[_{2}H{{e}^{4}}\] and\[\beta -\]particle is fast moving electron\[{{(}_{-1}}{{e}^{0}})\]When an\[\alpha -\]particle is emitted mass number decreases by 4 and atomic number by 2. Given, \[_{86}{{A}^{22}}{{\to }_{84}}{{B}^{210}}\] Decrease in mass number\[=222-210\]    \[=12\] \[\therefore \]Number of \[\alpha -\]particles\[=\frac{12}{4}=3\] \[\therefore \]After 3\[\alpha -\]particle atomic number \[=86-3\times 2=80\] So, increase is atomic number from 80 to 84 is 4. Therefore,\[4\beta \] particles as 1 \[\beta -\]particle increases the atomic number by 1.


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