Chapter 18, Problem 1SP

Interpretation Introduction

Interpretation:

Balanced nuclear equation for the production of plutonium-239 from uranium-238 has to be written.

Concept Introduction:

If the reaction occurs in the nucleus of an atom then it is known as nuclear reaction.  These reactions are not considered as ordinary chemical reactions because the electrons do not take part in reaction while the particle inside the nucleus does.  Isotope and nuclide are almost similar terms.  Isotopes refer to the same element that has different mass number while nuclide refers to atoms of same or different elements with specific atomic number and mass number.

This nuclear reaction can be represented by nuclear equation.  This is not a normal chemical equation.  Nuclear equation considers the mass number and atomic number of the reactants and products.  Unstable nucleus tends to emit radiation spontaneously.  During this process the nuclide is transformed into nuclide of another element.  Parent nuclide is the one which undergoes the radioactive decay.  Daughter nuclide is the one that is formed from parent nuclide after radioactive decay.

The radioactive decay can take place by emission of alpha particle, beta particle or gamma ray emission.  Alpha particle decay is a process in which an alpha particle is emitted.  This results in the formation of nuclide of different element that has atomic number that is 2 less and mass number that is 4 less than the original nucleus.  Beta particle decay is a process in which a beta particle is emitted.  This produces a nuclide of different element similar to that of alpha particle decay.  The mass number is same as that of parent nuclide while the atomic number increases by 1 unit.  Gamma ray emission is a process in which the unstable nucleus emits gamma ray.  This occurs along with alpha or beta particle emission.  The gamma rays are not shown in the nuclear equation because they do not affect balancing the nuclear equation.

Explanation of Solution

When uranium-238 undergoes reaction with a neutron, the mass number increases by 1 and there is no change in atomic number.  The formed product is uranium-239.  This can be represented as shown below,

    $\text{U}+\text{n}\stackrel{}{\to }\text{U}$

When a beta emission takes place, the mass number does not change while the atomic number is increased by 1.  Therefore, the formed product after beta emission of uranium-239 is neptunium-239.  This can be represented as shown below,

    $\text{U}\stackrel{}{\to }e+\text{N}\text{p}$

When a beta emission takes place, the mass number does not change while the atomic number is increased by 1.  Therefore, the formed product after beta emission of neptunium-239 is plutonium-239.  This can be represented as shown below,

    $\text{N}\text{p}\stackrel{}{\to }e+\text{P}\text{u}$

Balanced nuclear equations for the given conversions are written.