Electromagnetic radiation of wavelength 663 nm is just sufficient to ionise the atom of metal A. The ionization energy of metal A in kJ mol^-1 is \ \…

Electromagnetic radiation of wavelength $\displaystyle 663$ nm is just sufficient to ionise the atom of metal A. The ionization energy of metal A in $\displaystyle \mathrm{kJ} \mathrm{mol}^{-1}$ is \_\_\_\_. (Rounded-off to the nearest integer) $$\left[\mathrm{h}=6.63 \times 10^{-34} \mathrm{Js}, \mathrm{c}=3.00 \times 10^8 \mathrm{~ms}^{-1}, \mathrm{~N}_{\mathrm{A}}=6.02 \times 10^{23} \mathrm{~mol}^{-1}\right] $$