In Bohr series of lines of hydrogen spectrum, the third line from the red end corresponds to which one of the following inter-orbit jumps of the electron for Bohr orbits in an atom of hydrogen

The orbital angular momentum for an electron revolving in an orbit is given by $$\sqrt {l(l + 1)} {h \over {2\pi }}$$. This momentum for an s-electron will be given by

The number of d-electrons retained in Fe²⁺ (At no of Fe = 26) ion is :

According to the Periodic Law of elements, the variation in properties of elements is related to their