Atoms & Nuclei

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91 of 239

Question 91 of 239

Energy required for the electron excitation in Li++\mathrm{Li}^{++}from the first to the third Bohr orbit is :

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Answer: (B) 108.8eV108.8 \mathrm{eV}

En=−13.6Z2n2E_n=-13.6 \frac{Z^2}{n^2}
EL∗∗=−13.6×91=−122.4eVE_{\mathrm{L}}{ }^{* *}=-13.6 \times \frac{9}{1}=-122.4 \mathrm{eV}
EL∗∗=−13.6×99=−13.6eVE_{\mathrm{L}}{ }^{* *}=-13.6 \times \frac{9}{9}=-13.6 \mathrm{eV}
ΔE=−13.6−(−122.4)\Delta E=-13.6-(-122.4)
=108.8eV=108.8 \mathrm{eV}

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