The electron energy in hydrogen atom is given by `E_(n)=(-2.18xx10^(-18))//n^(2)J`. Calculate the energy required to remove an electron completely from the `n=2` orbit. What is the longest wavelength of light in cm that can be used to cause this transition?

Answer

`3647 Å`

Explanation

`E_i = - (2.18 xx 10^(-18))/(2^2) = 5.45 xx 10^(-19) J`
`E_f = 0`
`Delta E = 0 - (-5.45 xx 10^(-19)) = 5.45 xx 10^(-19) J`
`lambda = (hc)/(Delta E) = (6.626 xx 10^(-34) xx 3.0 xx 10^8)/(5.45 xx 10^(-19))`
`= 3.647 xx 10^(-7) "or" 3647 Å`