Atoms and Nuclei

Hydrogen $\left( {{}_1{H^1}} \right)$, Deuterium $\left( {{}_1{H^2}} \right)$, singly ionised Helium ${\left( {{}_2H{e^4}} \right)^ + }$ and doubly ionised lithium ${\left( {{}_3L{i^6}} \right)^{ + + }}$ all have one electron around the nucleus. Consider an electron transition from $n=2$ to $n=1.$ If the wavelengths of emitted radiation are ${\lambda _1},{\lambda _2},{\lambda _3}$ and ${\lambda _4}$ respectively then approximately which one of the following is correct?