Correct Answer - Option 3 :
Di-ionized Lithium
When an electron jumps from mth orbit to the nth orbit (m>n), the energy of the atom changes from Em to En. This extra energy (Em - En) is emitted as a photon of electromagnetic radiation. This corresponding wavelength is given as
\(\frac{1}{\lambda }\; = \;R{Z^2}\left( {\frac{1}{{{n^2}}} - \frac{1}{{{m^2}}}} \right)\)
Where R is the Rydberg constant = 1.0973 × 107 m-1
Now for the wavelength to be minimum the Z should be maximum. Out of given options, Z is maximum for Di-ionized Lithium.