GROUP 15 ELEMENTS
Atomic and ionic radii : Covalent and ionic radii increase down the group . There is appreciable increase in covalent radii from N to P . There is small increase from As to Bi due to presence of completely filled d or f orbitals in heavy elements .
10 . Ionisation energy : It goes on decreasing down the group due to increase in atomic size . Group 15 elements have higher ionisation energy than group 14 elements due to smaller size of group 15 elements . Group 15 elements have higher ionization energy than group 16 elements because they have stable electronic configuration i . e ., half filled p-orbitals .
11 . Allotropy : All elements of Group 15 except nitrogen show allotropy .
12 . Catenation : Nitrogen shows catenation to some extent due to triple bond but phosphorus shows catenation to maximum extent . The tendency to show catenation decreases down the group .
13 . Oxidation states : The common oxidation states are + 3 , + 5 , – 3 . The tendency to show – 3 oxidation state decreases down the group due to decrease in electronegativity which is due to increase in atomic size .
The stability of + 5 oxidation state decreases whereas stability of + 3 oxidation state increases due to inert pair effect .
Nitrogen shows oxidation states from – 3 to + 5 .
Nitrogen and phosphorus with oxidation states from + 1 to + 4 undergo oxidation as well as reduction in acidic medium . This process is called disproportionation .
3 HNO2 → HNO3 + H2O + 2 NO