Chapter 24, Problem 24.27P

Interpretation Introduction

Interpretation:

Reason for why Uranium and Thorium ore contains deposits of Helium has to be explained. Also the type of radioactive emission produces by these ore has to be given.

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. Also some of the rare earth elements like ${}^{114}Nd,{}^{ 146}Sm,\mathrm{...}{ }^{174}Hf$ and light elements like ${}^{8}Li,{ }^{{}^9}Li\mathrm{...}$ undergo $\alpha$ decay.