The radius of stationary state $(n=2)$ of hydrogen atom is $x \mathrm{pm}$. The radius of stationary state $(n=3)$ of $\mathrm{He}^{+}$ion (in pm) is

When electromagnetic radiation of wavelength 310 nm falls on the surface of a metal having work function 3.55 eV , the velocity of photoelectrons emitted is $x \times 10^5 \mathrm{~ms}^{-1}$. The value of $x$ is (Nearest integer) $\left(m_e=9 \times 10^{-31} \mathrm{~kg}\right)$

In which of the following options, elements are correctly arranged in the increasing order of their atomic radius?

$A, B C, D$ and $E$ are elements with atomic numbers 13 , $11,9,7$ and 16 respectively. Among these elements, ion of an element $X$ has largest size and ion of an element $Y$ has smallest size. $X$ and $Y$ are respectively.(Assume that all ions have nearest inert gas configuration)