The energy of an electron in the first Bohr orbit of hydrogen atom is $-2.18 \times 10^{-18} \ J$. Its energy in the third Bohr orbit is $........$.

Rutherford's experiment,which established the nuclear model of the atom,used a beam of

An electron initially present in an excited state of $H$ atom is further excited to another energy level by an incident photon. It releases $10$ photons while coming back to the ground state,out of which $7$ have higher energy than the incident photon. The electron was initially present in:

The ionization energy of a singly ionized helium ion $(He^+)$ is equal to:

Which of the following equations gives the angular momentum of an electron in a stationary orbit?

In the hydrogen spectrum,if an electron transitions from the $6^{th}$ orbit to the $3^{rd}$ orbit,what is the total number of spectral lines observed in the infrared region?