If the radius of the hydrogen atom is $53 \, pm$, the radius of the $He^{+}$ ion is closest to $...... \, pm$.

Which of the following electronic transitions in a hydrogen atom will require the highest energy?

Lifetimes of the molecules in the excited states are often measured by using pulsed radiation source of duration nearly in the nanosecond range. If the radiation source has the duration of $2 \, ns$ and the number of photons emitted during the pulse source is $2.5 \times 10^{15}$,calculate the energy of the source.

For a $Bohr$ atom,the angular momentum of an electron is given by $M(n = 1, 2, 3, .....)$ :

The energy levels for a hydrogen-like species with atomic number $Z$ can be given by:

An electronic transition in a hydrogen atom results in the formation of the $H_\alpha$ line of the hydrogen spectrum in the Lyman series. The energies associated with the electron in each of the orbits involved in the transition (in $kcal \ mol^{-1}$) are: