The energy of an $H$ atom in the $n^{th}$ orbit is $E_n$. What will be the energy of the $n^{th}$ orbit of a singly ionized helium atom $(He^+)$?

The potential energy of an electron in the hydrogen atom is $-6.8 \ eV$. Indicate in which excited state the electron is present.

Explain the following according to Bohr's model of hydrogen:
$(i)$ Principal quantum number
$(ii)$ Radius of stationary orbit $(r)$
$(iii)$ Energy of stationary state
$(iv)$ Isoelectronic ion of $H$
$(v)$ Velocity of electron

In the hydrogen spectrum,if an electron transitions from the $6^{th}$ orbit to the $3^{rd}$ orbit,what is the total number of spectral lines observed in the infrared region?

If the speed of an electron in the Bohr's first orbit of a hydrogen atom is $x$,the speed of the electron in the third Bohr's orbit is:

Based on the equation $\Delta E = - 2.0 \times 10^{-18} \, J \left( \frac{1}{n_2^2} - \frac{1}{n_1^2} \right)$,the wavelength of the light that must be absorbed to excite a hydrogen electron from level $n = 1$ to level $n = 2$ will be: $(h = 6.625 \times 10^{-34} \, J \, s, c = 3 \times 10^8 \, m \, s^{-1})$