GROUP 16 ELEMENTS
25. Oxidation states: They show-2, + 2, + 4, + 6 oxidation states. Oxygen does not show + 6 oxidation state due to absence of d – orbitals. Po does not show + 6 oxidation state due to inert pair effect.
The stability of-2 oxidation state decreases down the group due to increase in atomic size and decrease in electronegativity.
Oxygen shows-2 oxidation state in general except in OF2 and
O2F2
The stability of + 6 oxidation state decreases and + 4 oxidation state increases due to inert pair effect.
26. Ionisation enthalpy: Ionisation enthalpy of elements of group 16 is lower than group 15 due to half filled p-orbitals in group 15 which are more stable. However, ionization enthalpy decreases down the group.
27. Electron gain enthalpy: Oxygen has less negative electron gain enthalpy than S because of small size of O.
From S to Po electron gain enthalpy becomes less negative to Po because of increase in atomic size.
28. Melting and boiling point: It increases with increase in atomic number. Oxygen has much lower melting and boiling points than sulphur because oxygen is diatomic( O2) and sulphur is octatomic( S8).
29. Reactivity with hydrogen:
All group 16 elements form hydrides. Bent shape