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