Atoms and Nuclei

At a specific instant emission of radioactive compound is deflected in a magnetic field. The compound can emit
$\eqalign{ & \left( i \right)\,\,\,\,\,\,\,electrons\,\,\,\,\,\,\,\,\,\,\,\,\left( {ii} \right)\,\,\,\,\,\,\,protons \cr & \left( {iii} \right)\,\,\,H{e^{2 + }}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\left( {iv} \right)\,\,\,\,\,\,\,neutrons \cr} $

The emission at instant can be

If $13.6$ $eV$ energy is required to ionize the hydrogen atom, then the energy required to remove an electron from $n=2$ is

If ${N_0}$ is the original mass of the substance of half-life period ${t_{1/2}} = 5$ years, then the amount of substance left after $15$ years is