How many resonating structures possible for ${\mathrm{PO}}_4^{3-}$ ion is_____.

How many of the following violate the octet rule?

${\mathrm{SF}}_6, {\mathrm{PCl}}_3, {\mathrm{SCl}}_2, {\mathrm{BF}}_3, {\mathrm{BeCl}}_2, {\mathrm{CCl}}_4$

How many lone pairs are present in ${\mathrm{IF}}_7$?

How many of the following compound(s) contain(s) no covalent bond(s)?

$\mathrm{KCl}, \mathrm{KCN}, {\mathrm{PH}}_3, {\mathrm{O}}_2, {\mathrm{B}}_2{\mathrm{H}}_6, {\mathrm{CO}}_2 ,{\mathrm{H}}_2{\mathrm{SO}}_4$