Chapter 19, Problem 7A

Interpretation Introduction

Interpretation: The change in atomic number that is observed when an unstable nucleus produces a $\text{β}$ has to explained.

Concept introduction: In a nuclear reaction, unstable nuclide disintegrates into stable nuclide with emission of various radiations spontaneously. It is called radioactivity of nucleus. Emission of rays like alpha, beta and gamma rays occur in the process which changes the identity of nucleus.

During a nuclear change, an element undergoes change in its atomic mass or atomic number or both by emission of charged particles such as beta particle, alpha particle. Beta particle is one that has unit negative charge and alpha particle is one that has 2 unit positive charges and is equivalent to helium atom ${}_2^4\text{He}$ . Emission of proton, beta particle, alpha particle causes a change in atomic number of element.

Answer to Problem 7A

On emission of $\text{β}$ particle, atomic number increases by 1 unit.

Explanation of Solution

For reaction such as ${}_{90}^{231}\text{Th}\to \text{β}{+}_{91}^{231}\text{Pa}$ , $\text{β}$ particle is produced by ${}_{90}^{231}\text{Th}$ .From the reaction it can be seen that $\text{β}$ particle has 0 mass and 1 atomic number, so it is of nature of an electron.

Conclusion

On emission of $\text{β}$ particle, atomic number increases by 1 unit.