Chapter 24, Problem 24.144P

(a)

Interpretation Introduction

Interpretation:

Symbol for each isotope has to be written.

Concept Introduction:

Mass number is the net number of neutrons and protons present in a nucleus.

The elemental symbol of an element: ${}_{\text{Z}}^{\text{A}}\text{X =}{}_{\text{Atomic}\text{number}}^{\text{Mass}\text{number}}\text{X}$

(b)

Interpretation Introduction

Interpretation:

Mode of decay has to be predicted for nucleus 2 and 3.

Concept Introduction:

Nuclides that are unstable generally decay in a mode that changes its N/Z ratio to the band of stability.

• Nuclides having many neutrons (Neutron-rich nuclides) have a high N/Z ratio and lies above the band of stability. Therefore, to decrease N/Z ratio these nuclides undergo ${\beta }^{-}$ decay.
• Nuclides having many protons (Proton-rich nuclides) have a low N/Z ratio and lies below the band of stability. Therefore, to increase N/Z ratio these nuclides undergo $e^{-}$ capture and/or ${\beta }^{+}$ decay. Heavier elements mostly undergo $e^{-}$ capture whereas lighter elements undergo ${\beta }^{+}$ emission.
• Nuclides having $Z>83$ are considered as too heavy to be stable. To decrease the values of Z and N, it undergoes $\alpha$ decay.