JEE Main 2014 · 9 Apr · Shift 1 · Physics Q27

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PhysicsSingle correct+4 / -1Question 27 of 90

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

122.4 eV

30.6 eV

13.6 eV

3.4 eV

Answer and worked solution

Official answer: B

$E_n=-13.6\dfrac{Z^2}{n^2}$ eV. For $\ce{Li^2+}$ ( $Z=3$ ) in the first excited state ( $n=2$ ): $E=-13.6\times\frac94=-30.6$ eV. Removing the electron needs 30.6 eV.

Topics:Bohr model and hydrogen spectrum

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JEE Main 2014 · 9 Apr · Shift 1, Physics question 27