What is allotropy ? Explain the different allotropic forms of phosphours.

Explanation

Allotropy : The existance of an element in different physical forms having similar chemical properties is called allotropy.
`to` Allotropes of 'P' : `to` White 'P' (or) Yellow 'P'.
`to` Red 'P'
`to` Scarlet 'P'
`to` Violet 'P'
`to alpha` - black 'P'
`to beta` - black 'P'.
White phosphorus :
`to` It is poisonous and insoluble in water and soluble in carbon disulphide and glows in dark.
`to` It is a translucent white waxy solid.
`to` It dissolves in boiling NaOH solution and gives `PH_(3)`.
`P_(4)+3"NaOH"+3"H"_(2)to" PH"_(3)+underset("sodium hypo phosphite")(3"NaH"_(2)"PO"_(2)).`
`to` It is more reactive than other solid phases.
`to` Bond angle is `60^(@)` and it readily catches fire.
Red phosphorus :
`to` White 'P' `underset("for several days")underset("inert atmosphere")overset(573K)to` Red 'P'.
`to` Red 'P' `underset("high pressure")overset(Delta)to` Black 'P'.
`to` Red 'P' possesses iron grey lustre.
`to` In is odour less, non poisonous and insoluble in water as well as `CS_(2)`.
`to` Red 'P' is much less reactive than white 'P'.
Black 'P' :
`to alpha` - Black 'P' : It is formed when red 'P' is heated in a sealed tube 803K.
`to beta` - Black 'P' : It is prepared by heating white 'P' at 473 K under high pressure.