(a)Find the wavelength of the radiation required to excited the electron is `Li^(++)` from the first to the third Bohr orbit (b) How many spectral lines are observed in the emission spectrum of the above excited system?

Options

A. `108.8eV,3`
B. `13.6eV,4`
C. `54.4eV,2`
D. `10.2eV,3`

Answer

A

Explanation

(a) the energy in the first orbit =`E_(1)=Z^(2)E_(0)` Where ltbr. `E_(0)-13.6eV` is the energy of a hydrogen atom in ground state . Thus for `Li^(++)`, ltbr.` E_(1)=9E_(0) =9xx(-13.6eV)`ltbr. The energy in the third orbit is
` E_(3)=E_(1)/n_(2)=E_(1)/9=-13.6eV`
Thus , `E_(3)-E_(1) =108.8eV,(hc)/lambda=e_(a)-E_(1)`