Ratio of velocities of electrons of hydrogen atom in $1^{st}$,$2^{nd}$,$3^{rd}$ orbit is

Ionisation energy of $He^{+}$ is $19.6 \times 10^{-18} \, J \, atom^{-1}$. The energy of the first stationary state $(n = 1)$ of $Li^{2+}$ is

The energy of an electron in the first Bohr orbit of hydrogen atom is $-2.18 \times 10^{-18} \ J$. Its energy in the third Bohr orbit is $........$.

When an electron transitions from $n = 4$ to $n = 2$,the emitted spectral line will be ........

Calculate the ratio of the radius of the $2^{nd}$ and $3^{rd}$ orbit of a hydrogen atom. (Note: $r_n \propto n^2$)

If the radius of the electron orbit in the excited state of a hydrogen atom is $476.1 \ pm$, the energy of the electron in that excited state in $J$ is (Radius and energy of the electron in the first orbit of a hydrogen atom are $52.9 \ pm$ and $-2.18 \times 10^{-18} \ J$ respectively).