The size of an atom is of the order of

An alpha particle colliding with one of the electrons in a gold atom loses

In a Rutherford scattering experiment when a projectile of charge $z_1$ and mass $M_1$ approaches a target nucleus of charge $z_2$ and mass $M_2$, the distance of closest approach is $r_0$ The energy of the projectile is 

The number of completely filled shells for the element ${ }_{16} S ^{32}$ is

For a certain hypothetical one electron atom the wavelength (in $Å$ ) for the spectral lines for transition from $n = p$ to $n = 1$ are given by $\lambda  = \frac{{1500{p^2}}}{{{p^2} - 1}}$ (where $p > 1$ ), then the ionization potential of this element must be ......$V$ (Take $hc = 12420\ eV-Å$ )

The wavelengths of ${K_\alpha }$ $X-$ rays of two metals $'A'$ and $'B'$ $\frac{4}{{1875R}}$ and $\frac{1}{{675R}}$ respectively, where $'R'$ is Rydberg's constant. The number of elements lying between $'A'$ and $'B'$ according to their atomic numbers is