$A$ nucleus $_Z{X^A}$ emits $9 \alpha$-particles and $5 \beta$-particles. The ratio of total protons to neutrons in the final nucleus is:

When a nucleus with atomic number $Z$ and mass number $A$ undergoes a radioactive decay process:

In a radioactive sample,${ }_{19}^{40} K$ nuclei decay into stable ${ }_{20}^{40} Ca$ nuclei with a decay constant of $4.5 \times 10^{-10} \text{ per year}$ or into stable ${ }_{18}^{40} Ar$ nuclei with a decay constant of $0.5 \times 10^{-10} \text{ per year}$. Given that in this sample,all the stable ${ }_{20}^{40} Ca$ and ${ }_{18}^{40} Ar$ nuclei are produced by the ${ }_{19}^{40} K$ nuclei only. In time $t \times 10^9 \text{ years}$,if the ratio of the sum of stable ${ }_{20}^{40} Ca$ and ${ }_{18}^{40} Ar$ nuclei to the radioactive ${ }_{19}^{40} K$ nuclei is $99$,the value of $t$ will be: [Given $\ln 10 = 2.3$]

$A$ stationary nucleus of mass number $220$ emits an $\alpha$-particle. If the energy released in the process is $5.5 \, MeV$,find the kinetic energy of the $\alpha$-particle in $MeV$.

During negative $\beta$-decay,which of the following processes occurs?

Radioactivity is a/an ...... process.