What is the number of sigma bonds in $P_4O_{10}$?

The set of molecules in which the central atom does not obey the octet rule is

Fill in the blanks:
$(i)$ In $1927$,Heitler and London proposed the ........ theory.
$(ii)$ The ${\rm{ClF}}_3$ molecule has a .... shape.
$(iii)$ The number of bonding pairs in ions with a square planar shape is .......... .
$(iv)$ The value of the dipole moment in ${\rm{HBr}}$ is .......... .

How many $S-S$ bonds,$S-O-S$ bonds,$\sigma$-bonds,and $\pi$-bonds are present in the trimer of sulphur trioxide $(S_3O_9)$?

Which of the following species is isoelectronic with $N_2O$ and has the same structure?

The species having the maximum $Cl-O$ bond order is: