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

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