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?

Explanation

`Delta E = E_(oo) - E_2`
`= 0 - (-(2.18 xx 10^(-18) J "atom"^(-1))/(2))`
`= 5.45 xx 10^(-19) J "atom"^(-1)`
`Delta E = (hc)/(lambda) " or " lambda = (hc)/(Delta E)`
`:. lambda = ((6.626 xx 10^(-34) Js) xx (3.0 xx 10^(8) ms^(-1)))/(5.45 xx 10^(-19) J "atom"^(-1))`
`= 3.647 xx 10^(-7) m`
or `" " = 3.647 xx 10^(-5) cm`.