Which is the correct order of thermal stability for H2E (E = O, S, Se, Te and Po)? (NEET 2019) (a) H O H S H Se H Te H Po (b) H Po H Te H Se H S H O (c) H Se H Te H Po H O H S (d) H S H O H Se H Te H Po

For group 16 elements, the hydrides with higher molar mass (e.g. H2PO) are less thermally stable than hydride with lower molar mass (e.g. H2O). This is due to the increase in size of central atom which results to the weakening of M–H bond due to increased bond length. Thus, the correct order of thermal stability of H3E(E = O, S, Se, Te and Po) is as follows: 2 2 2 2 2 H Po H Te H Se H S H O