Properties of the elements are given below. Where would you locate the following elements in the periodic table?
$(a)$ An element which is an inert gas with atomic number $2$.
$(b)$ An element whose thin oxide layer is used to make other elements corrosion resistant by the process of 'anodising'.

Compare the radii of two species $X$ and $Y$. Give reasons for your answer.
$(a)$ $X$ has $12$ protons and $12$ electrons.
$(b)$ $Y$ has $12$ protons and $10$ electrons.

An element which is an essential constituent of all organic compounds belongs to :

Write the formulae of chlorides of Eka-silicon and Eka-aluminium,the elements predicted by Mendeleev.

$(a)$ Identify the element that has two completely filled shells and the number of valence electrons in each are as: $(i)$ $1$,$(ii)$ $2$,$(iii)$ $7$,$(iv)$ $8$. $(b)$ Analyse which amongst them is inert.

Given below are four elements with their atomic numbers:

Element	Atomic Number
$A$	$16$
$B$	$11$
$C$	$3$
$D$	$14$

$(a)$ Identify the elements which belong to the same group of the Modern Periodic Table.
$(b)$ Arrange the given elements in decreasing order of atomic size.
$(c)$ Write the formula of the oxide of $B$.
$(d)$ Which of the above elements is a metalloid?