The radius of the first Bohr's orbit of the hydrogen atom is ............. $\mathring{A}$.

For the Balmer series in the spectrum of $H$ atom,$\bar{v}=R_{H}\left\{\frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}}\right\}$,the correct statements among $(I)$ to $(IV)$ are:
$(I)$ As wavelength decreases,the lines in the series converge.
$(II)$ The integer $n_{1}$ is equal to $2$.
$(III)$ The lines of longest wavelength corresponds to $n_{2}=3$.
$(IV)$ The ionization energy of hydrogen can be calculated from wave number of these lines.

When an electron jumps from a lower to a higher orbit,its energy

The kinetic energy of an electron in the ground state of a $Be^{3+}$ ion is given by:

The energy of an electron in the first Bohr orbit of a hydrogen atom is $-13.12 \times 10^5 \ J \ mol^{-1}$. Calculate the energy required for the transition of an electron from the first orbit to the second orbit.

The maximum energy is possessed by an electron when it is present: