The radius of the electron in the first excited state of a hydrogen atom is:

Which one of the following is considered as the main postulate of Bohr’s model of atom?

If the threshold wavelength for a metal is $\lambda_0$ and the wavelength of incident light is $\lambda$,what will be the maximum velocity of the emitted electrons?

Binding energy of a hydrogen atom is $13.6 \ eV$. The binding energy of a singly ionized helium atom is : ............ $eV$

As an electron is brought from an infinite distance close to the nucleus of the atom,the energy of the electron-nucleus system :

If the ionization potential of $Li^{2+}$ is $122.4 \ eV$,what is the $5^{th}$ ionization potential of carbon in $eV$?