The ionisation energy of a H-like atom is `4R_(h)`
a. Calculate the wavelength of radiation emitted when an electron jumps from the first excited state to the ground state
b. What is the radius of first orbit of this atom?
Given `1R_h= 2.18 xx 10^(-19) J`

Answer

`303.89Å,2.645xx10^(-9) cm`

Explanation

(i) `(1)/(lambda)=(DeltaE)/(hc)=[(1)/(n_(1)^(2))-(1)/(n_(2)^(2))]`
`(1)/(lambda)=(4R)/(3R)[(1)/(1^(2))-(1)/(2^(2))]`
`lambda=(hc)/(3R)=303Å`
(ii) `DeltaE=13.6 Z^(2)`
`Z=2`
`r=(r_(0))/(Z)=2.645xx10^(-11)m`