A positive hydrogen like ion having electron at its ground state ejects it, if a photon of wavelengt

Question

A positive hydrogen like ion having electron at its ground state ejects it, if a photon of wavelength $228 \AA$ or less is absorbed by it. The atomic number of the ion is $\_\_\_\_$ .

Professor PC Thomas Classes · Answer

(2) B.E. of  last electron  \ $ E=13.6 	imes Z^2=\frac{h c}{\lambda} \Rightarrow Z^2=\frac{1.24 	imes 10^4}{13.6 	imes 228}=4 \Rightarrow Z=2 $