In the electronic structure of $H_2SO_4$,the total number of unshared electrons is

Which of the following have $X-O-X$ linkage? (where $X$ is the central atom):
$(i) \ Cr_2O_7^{2-}$
$(ii) \ S_2O_3^{2-}$
$(iii) \ \text{Pyrosilicate}$
$(iv) \ \text{Hyponitrous acid}$

If the structure of a stable molecule containing atoms of elements $X, Y$,and $Z$ is as shown in the figure,what could the elements $X, Y$,and $Z$ be respectively?

The number of $\sigma$ and $\pi$ bonds in peroxodisulphuric acid are,respectively

The pairs among $A = [SO_3^{2-}, CO_3^{2-}]$, $B = [O_2^{2-}, F_2]$, $C = [CN^-, CO]$, $D = [NH_3, H_3O^+]$ and $E = [MnO_4^{2-}, CrO_4^{2-}]$ that do not have similar Lewis dot structures are:

Number of electron-deficient molecules among the following $PH_{3}$,$B_{2}H_{6}$,$CCl_{4}$,$NH_{3}$,$LiH$,and $BCl_{3}$ is ..... .