Atoms & Nuclei

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83 of 239

Question 83 of 239

If the binding energy of the electron in a hydrogen atom is 13.6eV13.6eV, the energy required to remove the electron from the first excited state of Li++{Li}^{++} is :

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Answer: (D) 30.6eV30.6eV

Energy of an electron in nth orbit of an ion with atomic number zz is, E=−13.6×z2n2eVE=-13.6\times \dfrac{{z}^{2}}{{n}^{2}}eV

for 1st{1}^{st} excited state of Li++,z=3,n=2L{i}^{++},z=3,n=2

E=−13.6×32n2=−13.6×94eVE=-13.6\times \dfrac{{3}^{2}}{{n}^{2}}=-13.6\times \dfrac{9}{4}eV

=−30.6eV=-30.6eV

∴∴ Required energy =30.6eV=30.6eV

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