Chapter 11, Problem 11.81CP

a)

Interpretation Introduction

Interpretation:

The mode of radioactivity decay and it balanced nuclear reaction for $\text{I-131}$ has to be identified.

Concept Introduction:

Beta decay:

The $\text{β}$ emission includes the decomposition of a neutron to yield an electron and a proton.

${}_{\text{0}}^{\text{1}}\text{n}{\to }_{\text{1}}^{\text{1}}{\text{P+}}_{\text{-1}}^{\text{0}}\text{e}$

Where the electron $\left({}_{\text{-1}}^{\text{0}}\text{e}\right)$ is emitted as a $\text{β}$ particle and the proton is taken by the nucleus

Balanced nuclear reaction:

For a balanced nuclear equation the mass number and atomic number on the both sides of the reaction should be equal.

b)

Interpretation Introduction

Interpretation:

The fraction of $\text{I-131}$ remains after four weeks and eight weeks has to be calculated.

Concept Introduction:

Half-life:

The time required to reduce a radioactive isotope to half of its initial value.

For non-integral number:

For a non-integral number of half-lives, the fraction of radioisotope remaining is

$\text{fraction}\text{remaining=}{\left(\text{0}\text{.5}\right)}^{\text{n}}$