Which of the following species contains four lone pairs of electrons?

Total number of non-bonded electrons present in $NO_2^{-}$ ion based on Lewis theory is $........$

Which of the following does not obey the octet rule?

Compound $X$ is the anhydride of sulphuric acid. The number of $\sigma$ bonds and the number of $\pi$ bonds present in $X$ are respectively:

The number of $Cl=O$ bonds in perchloric acid is:

For the following species,determine whether the octet rule is obeyed or not obeyed. Provide the reason for each:
$(1) BeF_4^{2-}$
$(2) BF_3$
$(3) CO_2$
$(4) NO$
$(5) NH_3$