The energy of an electron in the $3^{rd}$ orbit of a hydrogenic atom is $-E$. The energy of an electron in the first orbit will be

The ionization energy of a hydrogen atom is $13.6 \ eV$. The energy required to ionize a hydrogen atom in its second excited state is ........... $eV$.

The Bohr radius of a hydrogen-like species is $70.53 \text{ pm}$. The species and the stationary state $(n)$ are respectively (Given: Hydrogen atom Bohr radius is $52.9 \text{ pm}$)

What is the maximum number of emission lines when the excited electron of an $H$ atom in $n=6$ drops to the ground state?

Calculate the wavenumber of a photon emitted during the transition from the orbit of $n=3$ to $n=2$ in a hydrogen atom. $(R_{H} = 109677 \ cm^{-1})$ (in $cm^{-1}$)

The work function $(W_0)$ of $Li, K, Mg, Ag$ and $Cu$ are $2.42, 2.25, 3.70, 4.30$ and $4.80 \ eV$ respectively. The number of metals which undergo photoelectric effect if a radiation of wavelength $540 \ nm$ falls on them is $(1 \ eV = 1.602 \times 10^{-19} \ J)$.