If the ionization energy of a hydrogen atom is $E$,then the ionization energy of $Li^{2+}$ will be ............ $E$.

The space between the proton and the electron in a hydrogen atom is:

$A$ bulb is rated at $150 \text{ W}$, converting $8\%$ of its energy into light. If the energy of one photon is $4.42 \times 10^{-19} \text{ J}$, how many photons are emitted by the bulb per second?

If the radius of an electron in the excited state of $He^{+}$ is $0.4232 \ nm$, the energy of the electron in that excited state in $J$ is: (The radius and energy of an electron in the first orbit of a hydrogen atom are $52.9 \ pm$ and $-2.18 \times 10^{-18} \ J$ respectively)

The energy of a photon is $3 \times 10^{-12} \ erg$. What is its wavelength in $nm$? $(h = 6.62 \times 10^{-27} \ erg \cdot s; \ c = 3 \times 10^{10} \ cm/s)$

When the electron passes from the energy state nearest to the nucleus to the third energy level,it will: