Question

A neutral lithium atom has three protons, three electrons and some neutrons (depending on the isotope). The modulus of energy of an electron in the 2nd orbit of a $L{i}^{++}$ ion is___ eV.

Answer 1

Applying the general expression for orbital energy for Z=3 and n=2,
$E_n=-13.6\times \frac{Z^2}{n^2}eV$
$\Rightarrow E_{n=2}^{Z=3}=-13.6\times \frac{3^2}{2^2}eV=-30.6eV.$