Chapter 19, Problem 3A

Interpretation Introduction

Interpretation: Implication of atomic number and mass number of a nucleus must be explained with an example.

Concept introduction: Nuclear reactions are those where an unstable nuclide disintegrates in order to form a stable nuclide with emission of various radiations feasibly. It is called radioactivity of nucleus. The particles or rays emitted during the process are alpha, beta and gamma rays which cause a change in the identity of nucleus.

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 ${}_2^4\text{He}$ .

Answer to Problem 3A

Atomic number indicated by Z is a count of protons or electron in a nucleus and mass number (A) is sum of proton and neutron contained in a nucleus.

Explanation of Solution

Atomic number indicated by Z is a count of protons or electron in a nucleus and mass number (A) is sum of proton and neutron contained in a nucleus. Change in Z causes change in identity of nucleus whereas mere change in A indicates isotopes of nucleus.

Such as in reaction this: ${}_{53}^{131}\text{I}{\to }_{-1}^0\text{e}+{}_{54}^{131}\text{Xe}$ , iodine has A as 131 and Z as 53 which after loss of 1 electron, its Z reduces to 54. With change in Z the identity of nucleus changes from iodine to Xenon.

Conclusion

Atomic number indicated by Z is a count of protons or electron in a nucleus and mass number (A) is sum of proton and neutron contained in a nucleus.