What is the nergy difference ( in kJ `mol^(-1)`) between the first and second shell fo H-atom if the first emission in the Lyman series occurs at ` lambda = 121.5` nm ?

Explanation

I line of Lyman series is due to ` E_(2) - E_(1) = Delta E`
` therefore Delta E //mol e = ( h.c.N_(A))/(lambda)`
`= (6.626 xx 10^(-34) xx 3 .0 xx 10^8 xx 6.023 xx 10^(23))/(121.5 xx 10^(-9))`
`= 9.85 xx 10^(5) "J mol"^(-1) = 985k "J mol"^(-1)`.