The total maximum number of electrons possible in $3 d$. $6 d, 5 s$ and $4 f$ orbitals with $m_l$ (magnetic quantum number) value -2 is

The radius of fourth orbit in $\mathrm{He}^{+}$ion is ' $R_1{ }^{\prime} \mathrm{pm}$ and radius of third orbit in $\mathrm{Li}^{2+}$ ion is ' $R_2{ }^{\prime} \mathrm{pm}$. The value of ( $R_1-R_2$ ) in pm is

The de-Broglie wavelengths of two fast moving particles $X, Y$ are $1 \mathrm{~nm}, 3 \mathrm{~nm}$ respectively. Mass of $X$ is nine times the mass of $Y$. The ratio of kinetic energies of $X, Y$ is

The difference between the radii of 3rd and 2nd orbit of H -atom is $x \mathrm{pm}$. The difference between the radii of 4th and 3rd orbit of $\mathrm{Li}^{2+}$ ion is $y$ pm. $y: x$ is equal to