Absoprtion specrum, identifying the 1 electon atom

[CV101]

Homework Statement

The energies of some transitions observed in the absorption spectrum of an unknown one electron ion ( eg He+) are listed. Given that these transitions originate from the lowest energy level suggest an identification of the unknown ion

UNKNOWN ION (CM^-1)
1646254.1
1560886.3
1316965.2

Homework Equations

ok, i am using Delta E = Rh (1/nf^2 - 1/ni^2) where f stands for final and i for initial

The Attempt at a Solution

the problem is that I am not getting numbers close to integer values. I am not sure if the q even requires a numerical answer, as 3 ionisation energies must mean that the element is Be. I really don't know where to start. pls help

 

[Borek]

These are "some transitions", so it is not a complete list of three ionization energies.

Obvious line of attack is to try to find Z from the data given.

 

[CV101]

How?

how would you find z? sorry, I have no clue