Question

The electron energy in hydrogen atom is given by E_n = (- 2.18 × 10^-18) / n² 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?

Answer 1

Step I.

Calculation of energy required 

The energy required is the difference in the energy when the electron jumps from orbit with n = ∞ to orbit with n = 2. 

The energy required (∆E) = E_∞ - E₂

Step II. 

Calculation of the longest wavelength of light in cm used to cause the transition 

∆E = hv = hc / λ.