A doubly ionized lithium atom is hydrogen like with atomic number 3. Find the wavelength of the radiation required to excite the electron in `Li^(++)` from the first to the third Bohr orbit (ionization energy of the hydrogen atom equals 13.6 eV).

Answer

(a) `(hc)/(13.6xx8e)=113.7Å` (b) `3`

Explanation

(a) `DeltaE= 13.6xx3^(2)xx((1)/(1)(1)/(3^(2)))eV`
`13.6xx8eV`
`lambda=(hc)/(DeltaE)=(12400)/(13.6xx8)Å=113.7Å`
(b) no. of spectral lines `= .^(n)C_(2)`
`= .^(3)C_(2)=3`