Question

Excitation energy of a hydrogen like ion in its excitation
state is 40.8 eV. Energy needed to remove the electron from
the ion in ground state is
(a) 54.4 eV (b) 13.6 eV (c) 40.8 eV (d) 27.2 eV

Answer 1

Explanation:

ANSWER

For a hydrogen atom like system the energy for nth level is given by En=n2−13.6Z2eV

So the ground state energy will be E1=1−13.6Z2eV

and for the state n=2 the energy is E2=4−13.6Z2eV

So the excitation energy foe this state will be E2−E1=10.2Z2eV

as it is given to be 40.8eV  so Z2=4 or Z=2

So the energy in ground state will be E1=−54.4eV

so the inonization energy will be −(−54.4eV)=54.4eV