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