Solve this:
Q. (d) Calculate the ionization energy of $L{i}^{2+}$. (Given that ionization energy of H is 13.6 eV.)

Dear Student,
To find the ionisation energy of a hydrogen like atom with one electron we use the formula
IE = 13.6Z²/n² eV , Where Z is atomic number and n is the shell number.
So Li has Z is 3 and n is 1( because hydrogen is having n=1)
So Ionisation energy of Li²+ = 13.6×3² /1 eV= 13.6 *9 eV =122.4 eV.