For `He^(+) and Li^(2+)`, the energies are related to the guantum number, n, through an expression `E_(n)= - (Z^(2)B)/(n^(2))`, where Z is the atomic number of species and `B=2.179 xx 10^(-18)J`
What is the energy of the level n=3 of a `Li^(2+)` ion?

Explanation

To find the energy of the level \( n = 3 \) for a \( \text{Li}^{2+} \) ion, we can use the formula provided:

\[ E_n = -\frac{Z^2 B}{n^2} \]

where:
- \( Z \) is the atomic number of the ion,
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