Trends in chemical reactivity of Group 15 elements

Chemical properties of Group 15 elements

1. Phosphorous exhibit covalent character though it can accept three electrons to form phosphides. The covalent character decreases as we move down the group. that is
Phosphorus (P) > Arsenic (As) > Antimony (Sb) > Bismuth (Bi)

2. Group 15 element Forming Hydrides

The element of group 15 form hydrides of the type MH₃. They are NH₃ (Ammonia), PH₃ (Phosphine), AsH₃ (Arsine), SbH₃ (Stibine) and BiH₃ (Bismuthine). Hydrides are covalent and central atom is sp³ hybridized. Due to the presence of lone pair on central atom, they act as lewis bases and has pyramidal shape. The basic strength of hydrides decreases down the group. Thermal stability of hydrides also decreases on moving down the group. Except NH₃ all the hydrides are strong reducing agents and react with metal ions. The reducing character increases in going from NH₃ to BiH₃.

3. Group 15 element Forming Halides

The group 15 elements form two series of halides of the type MX₃ and MX₅.Nitrogen does not form pentahalides because of the absence of d-orbitals in nitrogen. Trihalides are pyramidal in shape and the central atom is in sp³ hybridised state. In pentahalides of group 15 elements, the central atom is in sp³ d hybridization and has trigonal bipyramidal geometry. Phosphorus trichloride ( PCl₃) fumes in moist air because of its reaction with water producing HCl.

PCl₃ + 3H₂O ------------> H₃PO₃ + 3HCl

Phosphorus pentachloride (PCl₅) fumes in air beacuse it react with water to give initially POCl₃ and finally H₃PO₄

PCl₅ + H₂O -----------> POCl₃ + 2HCl

POCl₃ + 3H₂O -----------> H₃PO₄ + 3HCl


4. Group 15 element Forming Oxides

Nitrogen forms five oxides with oxidation state ranging from +1 to +5. They are N₂O (Nitrous oxide), NO (Nitric Oxide), N₂O₃ (Dinitrogen trioxide), N₂O₄ (Dinitrogen tetroxide) and N₂O₅ (Dinitrogen pentoxide). Other elements of group 15 form two types of oxides of the type M₂O₃ and M₂O₅ (M=P,Sb or Bi. Due to reluctance of P,As,Sb and Bi to form pie-pie multiple bonding, their oxides have cage like structure and exist as dimmers (M₄O₆ and M₄O₁₀).

For more chemistry article visit Trends in chemical reactivity of Group 14 elements