The radius of second orbit of hydrogen atom is same as that of orbit ( $n$ ) of an ion ( $x$ ), $n$ and $x$ are respectively.

An electromagnetic radiation of wavelength 331.5 nm is made to strike the surface of a metal. Electrons are emitted with a kinetic energy of $12 \times 10^5 \mathrm{~J} \mathrm{~mol}^{-1}$. The work function (in eV ) of the metal is $\left(h=6.63 \times 10^{-34} \mathrm{Js}, N_A=6 \times 10^{23} \mathrm{~mol}^{-1}\right)$

Match the following

$$ \begin{array}{llll} \hline & \text { List-I (Element) } & & \text { List-II (Block) } \\ \hline \text { (A) } & \mathrm{Cd} & \text { I } & f \text {-block } \\ \hline \text { (B) } & \mathrm{Eu} & \text { II } & s \text {-block } \\ \hline \text { (C) } & \mathrm{Se} & \text { III } & d \text {-block } \\ \hline \text { (D) } & \mathrm{Ba} & \text { IV } & p \text {-block } \\ \hline \end{array} $$

The correct answer is

In long form of periodic table an element ' $E$ ' has atomic number 78 . The period and group number of the element are $x$ and $y$ respectively. $(x+y)$ is equal to