How much energy is required to ionise a H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom



Q.14:- How much energy is required to ionise a H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom (energy required to remove the electron from n=1 orbit).

 

Answer:-



En = -21.8×10-19/n2 Jatom-1 
For ionization from 5th orbit, n= 5n= ∞

∴ ΔE = E2 E1 = -21.8×10-19×(1/n2 1/n12) = 21.8×10-19×(1/n1 1/n22)
   = 21.8×10-19×(1/5 1/∞) = 8.72×10-20 J
For ionization from 1st orbit, n= 1n= ∞
∴ ΔE’ = 21.8×10-19×(1/1 1/∞) = 21.8×10-19 J
ΔE’/ΔE = 21.8×10-19/8.72×10-20 = 25

Hence, 25 times less energy is required to ionize an electron in the 5th orbital of hydrogen atom as compared to that in the ground state.