Brief information about elements $\mathrm{W},\mathrm{X},\mathrm{Y}$ and $\mathrm{Z}$ is given below :
$\mathrm{W}$: It has two electron shells both of which are completely filled.
$\mathrm{X}$: It has three electron shells in total and there are four electrons in the valence shell.
$\mathrm{Y}$: It has three electron shells in total and the first and third shells have two electrons each.
$\mathrm{Z}$ : It has twice as many electrons in its second shell as in its first shell and the second shell is the valence shell.
Identify $\mathrm{W},\mathrm{X},\mathrm{Y}$ and $\mathrm{Z}$.

The given part of the periodic table represents the period $3$ containing elements $\mathrm{a}$ to $\mathrm{h}$

Which of the following statements is/are correct?
I. $\mathrm{a}$ and $\mathrm{b}$ form basic oxides while $\mathrm{c}$ forms amphoteric oxide.
II. $\mathrm{d}$ is a typical non-metal.
III. $\mathrm{h}$ exists in monoatomic form.
IV. $\mathrm{f}$ is a non-metal.

Brief information about the element $\mathrm{X}$  is given below :

The formulae of the sulphate and chloride of the element $\mathrm{X}$ are respectively

The positions of four elements $\mathrm{K},\mathrm{L},\mathrm{M}$ and $\mathrm{N}$ in the periodic table are shown below:

Which of the following statements about these elements is correct?
I. $\mathrm{K},\mathrm{L},\mathrm{M}$ and $\mathrm{N}$ are all metalloids.
II. $\mathrm{K}$ is a metal while $\mathrm{L},\mathrm{M}$  and $\mathrm{N}$ are non-metals.
III. Among these four elements, $\mathrm{K}$ is the smallest in size.
IV. $\mathrm{K}$ is a metal, $\mathrm{L}$ and $\mathrm{M}$ are metalloids, $\mathrm{N}$ is a non-metal.