If an electron and a positron annihilate,then the energy released is

$A$ radioactive nucleus has specific binding energy $E_{1}$. It emits an $\alpha$-particle. The resulting nucleus has specific binding energy $E_{2}$. Then

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?

What is the fundamental reason for the chemical energy produced in a chemical process?

$A$ nucleus of mass $M + \Delta m$ is at rest and decays into two daughter nuclei of equal mass $\frac{M}{2}$ each. The speed of light is $c$. The binding energy per nucleon for the parent nucleus is $E_1$ and that for the daughter nuclei is $E_2$. Then:

The binding energy per nucleon versus mass number curve for nuclei is shown in the figure. $W, X, Y$ and $Z$ are four nuclei indicated on the curve. The process that would release energy is