Question

Which of the following facts are inferred from the given N vs Z graph?

• A. For lighter stable nuclei $\frac{N}{Z}=1$
• B. For lighter stable nuclei $\frac{N}{Z}>1$
• C. For heavier stable nuclei $\frac{N}{Z}=1$
• D. For heavier stable nuclei $\frac{N}{Z}>1$

Answer 1

Answer: (A), (D)

For heavier stable nuclei $\frac{N}{Z}>1$

Let’s divide the graph roughly into two portions:
1. Lighter nuclei (less mass number)
2. Heavier nuclei (more mass number)
We see from the graph that for lighter nuclei the black dots (stable nuclei) fall in the region of $\frac{N}{Z}=1$
Also as the mass number increases i.e. we move from lighter nuclei towards the heavier nuclei, the black dots (stable nuclei) fall into the region where $\frac{N}{Z}$ ratio is increasing.
The Blue, Orange and Red part of the graph are the unstable nuclei

Don't get confused with the Beta emitters labeling done here. Actually these unstable nuclei tend to bring themselves at the line of stable nuclei by altering their $\frac{N}{Z}$ ratio by such decays. You will learn about them in the later nodes.