Question

Calculate the minimum amount of energy required to remove an electron from n = 2 completely. For hydrogen, the energy of electron is E = -2.18 × 10^-18 /n²J. Calculate longest wavelength of light which can be used in the above transition.

Answer 1

Given that the electron energy in hydrogen atom
E_n = (-2.18 × 10^-18)/n²J
Energy required for ionization from n = 2 is given by
∆E = E_∞ – E₁
= [0- [(2.18 × 10^-18)/ 4] J
= 0.545 × 10¹⁸ J
∆E = 5.45 × 10^-19 J
Now, λ = he/∆E
= (6.626 × 10^-34) (3 × 10⁸)/ 5.45 × 10^-19
= 3647 × 10^-10 m
= 3647 Å