Chapter 18, Problem 30QRT

(a)

Interpretation Introduction

Interpretation:

Balanced nuclear equation has to be written for Iodine-131 undergoing beta emission.

Concept Introduction:

Radioactive nuclides undergo disintegration by emission of radiation.  This is a natural transmutation reaction where the nuclide of one element is converted into nuclide of another element.  Radioactive decay happens naturally.  This can also be done artificially in the laboratory by means of bombardment reaction.  Bombardment reaction is the one where the target nuclei is hit by a small fast moving high-energy particle to give a daughter nuclide and a small particle such as proton or neutron.  This can be represented in form of a nuclear equation.  A balanced nuclear equation is the one in which the sum of subscripts on both sides are equal and sum of superscripts on both sides are equal.

(b)

Interpretation Introduction

Interpretation:

Mass of ${\text{Na}}^{\text{131}}\text{I}$ sample that remains after 32.2 days has to be calculated if the half-life of isotope is 8.04 days.

Concept Introduction:

For a radioactive isotope, the relative instability is expressed in terms of half-life.  Half-life is the time required for half of the given quantity of the radioisotope to undergo radioactive decay.  Half-life of the radioactive isotope is independent of the quantity of the radioactive isotope.  Half-life of a radioactive isotope can be expressed as,

    $t_{1/2}=\frac{\text{0}\text{.693}}{k}$