Solid $BeH_2$ and solid $BeCl_2$ differ in

In which of the following compounds is the octet rule not followed?

For the compound having the formula $GaAlCl_4$,the correct option from the following is:

$CO_3^{2-}$ anion has which of the following characteristics?

Which of the following is the correct set for $SiO_2$?

Fill in the blanks given below:
$(i)$ The attractive force which holds atoms,molecules,and ions together is called ......... .
$(ii)$ First of all,............ and ............ scientists provided detailed information about valency.
$(iii)$ In the structure of an atom,when only the electrons of the outermost shell participate,they are known as ............ .
$(iv)$ The symbol used to represent valence electrons in an atom is called ........ .