Phosphorus and its Allotropes



Allotropes of phosphorous

The allotropes of phosphorous are red, black and white phosphorous.


White phosphorous

White or yellow phosphorus () is prepared from bone ash.

(electric furnace method) 


Properties of white phosphorous

It is white-to-transparent and soft waxy solid.
It is soluble in but insoluble in water.
It glows in dark due to slow oxidation producing yellowish-green light.


Red phosphorous

When white phosphorus is heated in the atmosphere of or coal gas at , red phosphorous is produced.
It has more atoms linked together in a network than white phosphorus does, which makes it much more stable. It is not quite as flammable, but given enough energy it still reacts with air. For this reason, we now use red phosphorus in matches.


Properties of red phosphorous

  • It is a reddiish-voilet crystalline solid.
  • It is stable in air
  • It is less reactive than white phosphorous and does not dissolve in liquid .
  • It is polymeric substance and form chain like structure.


Black phosphorous

The most stable form of phosphorous is black phosphorous. It has two forms: -phosphorous and -phosphorous.


Properties of black phosphorous

It has two forms: black phosphorous and black phosphorous. It can be sublimed in the air and has opaque monoclinic or rhombohedral crystals. It is very stable allotrope of phosphorous. It does not conduct electricity. It is highly polymerised form of phosphorous and has black metallic lustre.


Reactivity of allotropes of phosphorus

White phosphorus is the most reactive while black phosphorus is the least reactive. Therefore, white phosphorus is stored under water to protect it from air while red and black are stable in air.

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