Question

Explain the comparison of the reactivity of allotropes of phosphorus?

Answer 1

Allotropy

1. Allotropy is the property of some of the chemical elements in which they exist in two or more different forms but in the same physical state.
2. Example of elements that show allotropy is Carbon (C) and Phosphorus (P).

Allotropes of Phosphorous

Phosphorous exists in three allotropic forms:

1. White Phosphorous
2. Black Phosphorous
3. Red Phosphorous

Reactivity of allotropes of Phosphorus:-

Property	White phosphorus	Red phosphorus	Black phosphorus
Color	White	Dark red	Black
State	Waxy solid	Brittle powder	Crystalline and amorphous
Density	1.84 g/cm3	2.1 g/cm3	2.34 g/cm3
Ignition temperature	307 K	533 K	673 K
Melting point	317 K	Doesn’t melt	860 K

Therefore, white Phosphorus is the most reactive followed by red Phosphorus which is moderately reactive, and black Phosphorus is the least reactive from all three, White P> Red P > Black P.