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

Explanation

wavelength, `lambda=242 nm=242xx10^(-9) m`
Energy//photon of `lambda_(242 nm)=(hc)/(lambda)`
`=(6.6xx10^(-34)J sxx3.0xx10^(8) m s^(-1))/(242xx10^(-9) m)`
`=0.0821xx10^(-17) J atm^(-1)`
Since this energy is sufficient to cause ionisation of one atom of Na.
Therefore energy for `1` mole
`=(0.0821xx10^(-17)xx6.02xx10^(23))/(1000)`
`=494 kJ mol^(-1)`