Chapter 19, Problem 9A

Interpretation Introduction

Interpretation: A positron along with mass number and charge has to be given. The change in mass number and atomic number of nucleus when a positron is produced has to be explained.

Concept introduction: A subatomic particle whose mass is similar to that of electron and numerically equal but has a positive charge is called as a positron.

Answer to Problem 9A

Positron is a subatomic particle that has a positive charge and same mass of electron.

The mass of positron is zero and the charge on positron is positive.

When a nucleus $X$ emits a positron, the mass number remains A and the atomic number becomes Z-1.

Explanation of Solution

Positron particles are electrons with positive electric charge. Decay of Positron takes place when nucleus has too many protons or neutrons. The proton or neutron is transformed into one-another.

The mass of positron is zero and the charge on positron is positive.

The decay of a nucleus by emitting a positron $\left({\text{e}}^{\text{+}}\right)$ is called as positron emission. In positron emission, one proton of original nucleus decays to a form positron and a neutron.

The general equation is,

  $X\to e+Y$

Where,

• $A$ is the mass number.
• $Z$ is the atomic number.
• $X$ is the original isotope.
• $Y$ is the new isotope.

Example: Phosphorus-30 undergoes positron emission to silicon-30.

The balanced nuclear equation of $\text{P}$ to produce a positron is,

  $\text{P}\to e+\text{S}\text{i}$

Conclusion

Positron is an electron with positive charge. The mass of a positron is same as the mass of an electron that is zero and When a nucleus $X$ emits a positron, the mass number remains A and the atomic number becomes Z-1.