The ratio of the velocity of an electron in the second orbit of $He^{+}$ to the third orbit of $B^{4+}$ is:

The value of Planck's constant is $6.63 \times 10^{-34} \, J \cdot s$ and the speed of light is $3.0 \times 10^8 \, m \cdot s^{-1}$. The wavelength of a quantum of light with a frequency of $8 \times 10^{15} \, s^{-1}$ is closest to which of the following values in meters?

The total energy of the electron of $H$ atom in the second quantum state is $-E_2$. The total energy of the $He^{+}$ ion in the third quantum state is

The ratio of the energy of the $He^{+}$ ion in its first and second excited states will be:

What is the ratio of the radii of the second orbit for $H$,$He^{+}$,and $Li^{2+}$?

The potential energy of an electron in an atom is given by: