According to Bohr's Model for the Hydrogen atom, the energy of an electron in the $n^{th}$ shell is: $E_n=-\frac{13.6}{n^2}\text{ eV/atom}$ Given $n=3$ for the third orbit: $E_3=-\frac{13.6}{3^2}=-\frac{13.6}{9}\approx -1.51\text{ eV}$

• The negative sign indicates that the electron is bound to the nucleus by attractive forces.
• As $n$ increases, $E_n$ becomes less negative, meaning the electron is less tightly bound.