Question

iodine-131 is used to treat thyroid cancer. as iodine-131 decays, it emits radiation that can pass through aluminium foil, and a negatively charged particle. select the nuclear reaction that describes this process. \\(\ce{_{53}^{131}i \
ightarrow _{-1}^0e + _0^0\gamma + _{54}^{131}xe}\\) \\(\ce{_{53}^{131}i \
ightarrow _2^4he + _{51}^{127}sb + _0^0\gamma}\\) \\(\ce{_{53}^{131}i \
ightarrow _{52}^{127}te + _2^4\alpha + _{-1}^0\beta}\\) \\(\ce{_{53}^{131}i \
ightarrow _2^4\alpha + _{-1}^0e + _{52}^{127}te}\\)

Explanation:

Step1: Recall Beta Decay Rules

In beta - decay ($\beta^-$ decay), a neutron in the nucleus is converted into a proton, an electron ($_{-1}^0e$) and an antineutrino ($_0^0\overline{
u}$ or sometimes represented as $_0^0\gamma$ for simplicity in some notations). The general formula for $\beta^-$ decay is $_{Z}^{A}X
ightarrow_{Z + 1}^{A}Y+_{-1}^0e+_0^0\gamma$. For iodine - 131 ($_{53}^{131}\text{I}$), when it undergoes $\beta^-$ decay, the atomic number $Z$ increases by 1 (since a neutron turns into a proton), and the mass number $A$ remains the same. The product should have $Z = 53+ 1=54$, so the element is xenon (Xe) with mass number 131. So the reaction is $_{53}^{131}\text{I}
ightarrow_{-1}^0e+_0^0\gamma+_{54}^{131}\text{Xe}$.

Step2: Analyze Other Options

• For the option with $_{2}^{4}\text{He}$ (alpha particle), alpha decay changes the mass number by 4 and atomic number by 2, which does not match the behavior of iodine - 131 decay as it emits a negatively charged particle (beta particle, not alpha).
• The option with $_{52}^{127}\text{Te}$ and other particles has incorrect mass and atomic number conservation for a simple beta - like process.
• The option with multiple particles including alpha and beta is also incorrect as iodine - 131 undergoes beta decay (emission of $_{-1}^0e$) mainly in this context.

Answer:

The nuclear reaction $\ce{_{53}^{131}I
ightarrow _{-1}^0e + _0^0\gamma + _{54}^{131}Xe}$ (the first option among the four reaction boxes, considering the standard beta - decay of iodine - 131)