Boiling and melting points increase with an increase in atomic number down the group.
The large difference between the melting and boiling points of oxygen and sulphur may be explained on the basis of their atomicity: oxygen exists as diatomic molecule (O2) whereas sulphur exists as polyatomic molecule (S8).
Oxidation states and trends in chemical reactivity#
The elements of Group 16 exhibit a number of Oxidation states.
The stability of -2 oxidation state decreases down the group.
Since electronegativity of oxygen is group. high, it shows only negative oxidation states -2 except in the case of OF2 where it shows +2 oxidation state.
Other elements of the group exhibit oxidation states of +2, +4 and +6.
Sulphur (s), Selenium (se), Tellurium (Te) usually exhibit +4 oxidation state in their compounds with oxygen and +6 with fluorine.
The stability of + 6 oxidation state decreases down the group and that of +4 oxidation state increases due to inert pair effect.
Bonding in +4 and +6 oxidation states is primarily covalent.
Oxygen shows anomalous behaviour in its group due to its small size, high electronegativity and non-availability of d-orbitals in its valence shell.
One typical example of effects of small size and high electronegativity is the presence of strong hydrogen bonding in H2O which is not found in and H2S.