Chapter 16, Problem 4TS

Uranium- $238$ absorbs a neutron and then emits a beta particle. Show that the resulting nucleus is neptunium- $239$.

To determine

The resulting nucleus is neptunium-$239$ after uranium-$238$ absorbs a neutron and emits a beta particle.

Answer to Problem 4TS

Tthe neutron number becomes $146$ and the proton number becomes $93$ making the mass number $239$, which results in the nucleus is neptunium-$239$.

Explanation of Solution

The atomic number of uranium is $92$. Since the atomic number is the same as the number of protons, uranium-$238$ contains $92$ protons.

The mass number of uranium-$238$ is $238$. Since the mass number is the sum of protons and neutrons, so the number of neutrons in uranium-$238$ is 146.

When uranium-$238$ absorbs a neutron, its neutron number becomes $147$. In the emission of a beta particle, a neutron is converted into a proton and emits an electron. Thus, uranium-$238$ loses a neutron and gets a proton in beta emission. Thus the neutron number becomes $146$ and the proton number becomes $93$ making the mass number $239$. $93$ is the atomic number of neptunium. So, uranium-$238$ has converted to neptunium- $239$.

Conclusion

Therefore, the neutron number becomes $146$ and the proton number becomes $93$ making the mass number $239$, which results in the nucleus is neptunium-$239$.