The shortest wavelength transition in the paschen series in hydrogen occurs at 821 nm. So, at what wavelength does it occur ain Li2+ (isoelectronic of hydrogen)??? The options for the above question are:- a) 91.2 nm , b)273.6 nm , c)821.0 nm , d)7389.o nm........... Which of the options is correct and how please explain in detail..

Asked by Pragnya Kar | 29th May, 2014, 12:40: PM

Expert Answer:

Ans: (a) 91.2 nm

The shortest wavelength transition in the Paschen series in hydrogen occurs at 821 nm. According to the equation, the allowed energies of one electron atoms and ions are propotional to Z2, so we can expect the frequencies of the transitions between the same two levels to scale as Z2 too. Because wavelength is inversely propotional to the frequency. It follows that the wavelength of the transition should scale as 1/Z2. Therefore, the same transition in Li2+ (For which Z=3) can be expected to lie at = 91.2 nm

Answered by Hanisha Vyas | 29th May, 2014, 01:18: PM