Q140 / 200 · NEET 2009 (Screening) · Physics

In the nuclear decay given below $$ { }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X} \longrightarrow{ }_{\mathrm{Z}+1}^{\mathrm{A}} \mathrm{Y} \longrightarrow{ }_{\mathrm{Z}-1}^{\mathrm{A}-4} \mathrm{~B}^* \longrightarrow{ }_{\mathrm{Z}-1}^{\mathrm{A}-4} \mathrm{~B} \text {, } $$ the particles emitted in the sequence are

  • Correct answer
    A
    $\beta, \alpha, \gamma$
  • B
    $\gamma, \beta, \alpha$
  • C
    $\beta, \gamma, \alpha$
  • D
    $\alpha, \beta, \gamma$

Solution

Key Idea In a nuclear reaction conservation of charge number and mass number must hold good. Alpha particles are positively charged particles with charge $+2 e$ and mass $4 \mathrm{~m}$. Emission of an $\alpha$-particle reduces the mass of the radionuclide by 4 and its atomic number by 2. $\beta$-particles are negatively charged particles with rest mass as well as charge same as that of electrons. $\gamma$-particles carry no charge and mass. Radioactive transition will be as follows $$ \begin{aligned} & { }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X} \longrightarrow{ }_{\mathrm{Z}+1}{ }^{\mathrm{A}} \mathrm{Y}+\beta_{-1}^0 \\ & { }_{\mathrm{Z}+1}^{\mathrm{A}} \mathrm{Y} \longrightarrow{ }_{\mathrm{Z}-1}^{\mathrm{A}-4} \beta+\alpha_2^4 \\ & { }_{\mathrm{Z}+1}^{\mathrm{A}-4} \beta \longrightarrow{ }_{\mathrm{Z}-1}^{\mathrm{A}-4} \mathrm{\beta}+\gamma_0^0 \\ & \end{aligned} $$

Hence, the correct answer is option: 'A'.

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