Discuss the physical properties of group-$16$ elements.

(N/A) $(i)$ Atomicity: Oxygen is a diatomic gas,while other elements are polyatomic solids. For example,sulphur,selenium,and tellurium exist as polyatomic molecules such as $S_{8}$,$Se_{8}$,etc. This is due to the tendency of oxygen to form $p\pi-p\pi$ bonds because of its small size and high bond enthalpy of the $(O=O)$ bond.
$(ii)$ Metallic character: Down the group,the metallic character of the elements increases. Oxygen and sulphur are non-metals,selenium and tellurium are metalloids,whereas polonium is a metal. Polonium is radioactive with a half-life period of $13.8 \ days$.
$(iii)$ Melting and boiling points: The melting and boiling points gradually increase down the group. The large difference between the melting and boiling points of oxygen and sulphur is due to their atomicity; oxygen is diatomic,whereas sulphur is polyatomic.
$(iv)$ Allotropy: All elements of group-$16$ exhibit allotropy.