The energy of an electron in the $n^{th}$ orbit of a hydrogen atom is given by $E_n = - \frac{13.6}{n^2} \ eV$. How much energy in $eV$ is required to move an electron from the first orbit to the third orbit?

If the binding energy of the electron in a hydrogen atom is $13.6 \ eV$,then the energy required to remove the electron from the first excited state of $Li^{2+}$ is: (in $eV$)

$\frac{x}{x+4}$ is the ratio of energies of photons produced due to the transition of an electron of a hydrogen atom from its $(i)$ third permitted energy level to the second level and $(ii)$ the highest permitted energy level to the second permitted level. The value of $x$ will be.

In a sample of hydrogen-like atoms,all of which are in the ground state,a photon beam containing photons of various energies is passed. In the absorption spectrum,five dark lines are observed. The number of bright lines in the emission spectrum will be (assume that all transitions take place).

The ground state energy of a hydrogen atom is $-13.6 \text{ eV}$. When its electron is in the first excited state,its excitation energy is:

What is the ground state of an atom? And what is the ionization energy and excitation energy of a hydrogen atom?