An electron drops from the L shell to the K shell and gives off an X-ray with a wavelength of 0.0205 nm.

Question

What is the atomic number of this atom?

Answer 1

If the atom were hydrogen, you would be getting the Lyman alpha line, with a wavelength of 121.6 nm. The observed wavelength is 5932 times less. Take the square toot of that for the atomic number, which would be 77.

Answer 2

I meant square root, not toot.