How many quanta of different energy can be emitted by a hydrogen atom if the electron is in the third orbit? - Justify.

The value of ground state energy of hydrogen atom is $-13.6\mathrm{eV}$. What does the negative sign signify?

The value of ground state energy of hydrogen atom is $-13.6\mathrm{eV}$. How much energy is required to take an electron in this atom from the ground state to the first excited state?

Find the energies of photons produced due to the transition of an electron of the hydrogen atom from its

second permitted energy level to the first level and