An Electromagnetic radiation of wavelength `242` nm is just sufficient to ionise a sodium atom .Calculate the ionisation energy of sodium in `KJ mol^(-1)`.

Explanation

Energy associated with a photon of `242 nm`
`= (6.625 xx 10^(34) xx 3.0 xx 10^(8))/(242 xx 10^(-9))`
`= 8.21 xx 10^(-19) J`
`1` atom of Na for ionisation requires `= 8.21 xx 10^(-19) J` for ionistion
`6.023 xx 10^(23)` atoms of Na for ionisation required
`= 8.21 xx 10^(-19)xx 6.025 xx 10^(23)`
`49.45 xx 10^(4) J 494 .5 kJ mol^(-1)`