Which of the following is the outermost shell for elements of period $2$?

State whether the following statements are true or false: In the Modern Periodic Table,a zig-zag line separates metals from non-metals. The borderline elements—boron,silicon,germanium,arsenic,antimony,tellurium,and polonium—are intermediate in properties and are called metalloids or semimetals.

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

Taking the example of an element of atomic number $16$, explain how the electronic configuration of the atom of an element relates to its position in the modern periodic table and how valency of an element is calculated on the basis of its atomic number.

The following table shows elements represented by the letters $A, B, C, D, E, F, G$ and $H$.

Group	$1$	$2$	$13$	$14$	$15$	$16$	$17$	$18$
Element	$A$	$B$	$C$	$D$	$E$	$F$	$G$	$H$

$(i)$ Which of the elements has the atomic size:
$(a)$ biggest and $(b)$ smallest?
$(ii)$ Which element has valency:
$(a)$ $3$ and $(b)$ zero?

$(a)$ In this ladder (Figure),symbols of elements are jumbled up. Rearrange these symbols of elements in the increasing order of their atomic number in the Periodic Table.
$(b)$ Arrange them in the order of their group also.