Atoms and Nucle...

The nucler of which of following Pairs of nuclei are isotones

when u-238 nucleus originally at lest decay by emitting an α -particle having a speed u the recoil speed of the resi - dual nucleus is.

The energy difference between the first two levels of hydrogen atom is 10.2 eV. what is the corresponding energy difference for a singly ionised helium atom?

If in nature there may not be an element for which the principal quantum number n > 4, then the total possible number of elements will be

In the following atoms and molecules for the transition from n = 2 to n = 1, the spectral line of minimum wavelength will be produced by

First Bohr radius of an atom with Z = 82 is R. Radius of its third orbit is

The size of an atom is of the order of

Which one of the series of hydrogen spectrum is in the visible region?

The spectral series of the hydrogen atom that lies in the visible region of the electromagnetic spectrum

The kinetic energy of the electron in an orbit of radius r in hydrogen atom is (e = electronic charge)