The radius of the $$\mathrm{2^{nd}}$$ orbit of $$\mathrm{Li^{2+}}$$ is $$x$$. The expected radius of the $$\mathrm{3^{rd}}$$ orbit of $$\mathrm{Be^{3+}}$$ is

The number of s-electrons present in an ion with 55 protons in its unipositive state is

The magnetic moment of a transition metal compound has been calculated to be 3.87 B.M. The metal ion is

It is observed that characteristic X-ray spectra of elements show regularity. When frequency to the power "n" i.e. $${v^n}$$ of X-rays emitted is plotted against atomic number "Z", following graph is obtained.

The value of 'n' is :