Binding energy per nucleon of ${ }_1^2 H$ and ${ }_2^4 He$ are $1.1 \ MeV$ and $7.0 \ MeV$ respectively. Energy released in the process ${ }_1^2 H + { }_1^2 H \rightarrow { }_2^4 He$ is: (in $MeV$)

The binding energies of $_1H^2$,$_2He^4$,$_{26}Fe^{56}$,and $_{92}U^{235}$ are $2.22 \ MeV$,$28.3 \ MeV$,$492 \ MeV$,and $1786 \ MeV$ respectively. Which nucleus is the most stable?

The mass of a $H$-atom is less than the sum of the masses of a proton and an electron. Why is this?

$A$ nucleus of mass $ 20 u $ emits a $ \gamma $ photon of energy $ 6 MeV $. If the emission is assumed to occur when the nucleus is free and at rest, then the nucleus will have a kinetic energy nearest to (take $ 1 u = 1.6 \times 10^{-27} kg $): (in $keV$)

If the binding energy of $N^{14}$ is $7.5 \text{ MeV}$ per nucleon and that of $N^{15}$ is $7.7 \text{ MeV}$ per nucleon, then the energy required to remove a neutron from $N^{15}$ is (in $\text{ MeV}$)

The figure shows a plot of binding energy per nucleon $E_b$ against the nuclear mass $M$. $A, B, C, D, E, F$ correspond to different nuclei. Consider four reactions:
$(i) \, A + B \to C + \varepsilon$
$(ii) \, C \to A + B + \varepsilon$
$(iii) \, D + E \to F + \varepsilon$
$(iv) \, F \to D + E + \varepsilon$
where $\varepsilon$ is the energy released. In which reactions is $\varepsilon$ positive?