Answer:
-3.4 eV ([tex]-5.4\cdot 10^{-19} J[/tex])
Explanation:
In a hydrogen atom, the energy of an electron is given by:
[tex]E_n = - 13.6 eV \frac{1}{n^2}[/tex]
where
n is the principal quantum number
For an electron in the 2s orbital,
n = 2
So substituting this value into the formula, we find
[tex]E_2 = -13.6 eV \frac{1}{2^2}=-3.4 eV[/tex]
And converting this into Joules, we have
[tex]E_2 = -3.4 eV \cdot 1.6\cdot 10^{-19} J/eV=-5.4\cdot 10^{-19} J[/tex]
