Final answer:
The energy of the photon required to excite an electron from n=2 to n=5 in a He ion is approximately 11.06 eV or 1.77 x 10^-18 J.
Step-by-step explanation:
To calculate the energy of a photon required to excite an electron from n=2 to n=5 in a He ion, we can use the formula E = -13.6 eV * (1/n² - 1/nᵢ²), where n is the final energy level and nᵢ is the initial energy level.
Substituting the values, we get E = -13.6 eV * (1/5² - 1/2²).
Simplifying the equation gives us E = -13.6 eV * (1/25 - 1/4).
Evaluating the expression further gives E = -13.6 eV * (0.96 - 0.25).
Therefore, the energy of the photon required to excite an electron from n=2 to n=5 in a He ion is approximately 11.06 eV.
To convert this value to joules, we can use the conversion factor 1 eV = 1.6 x 10^-19 J.
Therefore, the energy of the photon required to excite the electron is approximately 1.77 x 10^-18 J.