Among the following, the number of aromatic compound(s) is

The correct statement(s) about the oxoacids, $$HCl{O_4}$$ and $$HClO$$ is (are)

The color of the $${X_2}$$ molecules of group $$17$$ elements changes gradually from yellow to violet down the group. This is due to

A crystalline solid of a pure substance has a face-centered cubic structure with a cell edge of $$400$$ $$pm.$$ If the density of the substance in the crystal is $$8$$ $$g\,c{m^{ - 3}},$$ then the number of atoms present in $$256$$ $$g$$ of the crystal is $$N \times {10^{24}}.$$ The value of $$N$$ is