Question

What is the energy in eV required to excite the electron from n = 1 to n = 2 energy level in a hydrogen atom? (n = principal quantum number)

• A. 13.6
• B. 3.4
• C. 17
• D. 10.2

Answer 1

The correct option is D 10.2

We know that, energy of an electron$=-13.6\frac{Z^2}{n^2}eV$
As the atom is hydrogen, Z = 1
To excite an electron from n = 1 to n = 2, energy would be absorbed.
Taking the difference between two energy states, we get
$\Delta E=E_f-E_i$
Therefore putting n = 1 and n = 2 and Z = 1,
$\Delta E=E_2-E_1$
$=-13.6\left(\frac{Z^2}{2^2}\right)-(-13.6\frac{Z^2}{1^2})eV$
$=-13.6(\frac{1}{2^2}-\frac{1}{1^2})eV$
$=(-13.6)\times (-0.75)=10.2eV$