In the absorption spectrum of $Na$,the missing wavelength$(s)$ are:

The spectrum obtained from a sodium vapour lamp is an example of

The spectrum of iodine gas under white light will be:

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be

When the potential energy of the second excited state of an atom is $108.8 \ eV$,the recoil momentum of the atom is ...... $kg \ m/s$.

Given below are two statements:
Statement $I$: Atoms are electrically neutral as they contain equal number of positive and negative charges.
Statement $II$: Atoms of each element are stable and emit their characteristic spectrum.
In the light of the above statements,choose the most appropriate answer from the options given below.