Question

A plot of the number of neutrons (n) against the number of protons (p) of stable nuclei exhibits upward deviation from linearity for atomic number, Z> 20. For an unstable nucleus having n/p ratio less than 1, the possible mode(s) of decay is (are)

• A. ${\beta }^{-}$ - decay ($\beta$ - emmision)
• B. orbital of K - electron capture
• C. neutron emission
• D. ${\beta }^{+}$ - decay (positron emission)
  

Answer 1

Answer: (B), (D)

${\beta }^{+}$ - decay (positron emission)




For elements, z> 20,
Generally Neutrons (n) > Protons (p)
$\Rightarrow \frac{n}{p}>1\Rightarrow$ upward deviation
In question, $\frac{n}{p}<1\Rightarrow$ Lesser neutrons
Now,
${\beta }^{-}-emission{\Rightarrow }_0^{1}n\to {}_{-1}^{0}e+{}_1^{1}H$
K- electron capture $\Rightarrow {}_1^{1}p+{}_{-1}^{0}e\to {}_0^{1}n$
Newton emission
${\beta }^{+}-emission{\Rightarrow }_1^{1}P\to {}_0^{1}n+{}_{+1}e$