Q.Write main differences between the properties of white phosphorus and red phosphorus.

Step 1: Structure.

White phosphorus consists of discrete, individual tetrahedral $P_4$ molecules held together only by weak van der Waals forces. Red phosphorus has a polymeric structure — chains of $P_4$ tetrahedra linked together by covalent P–P bonds, giving an iron-network-like solid.

Step 2: Physical properties.

Step 3: Chemical reactivity/stability.

White phosphorus is highly reactive — it catches fire spontaneously in air at about 30°C (hence stored under water) — because the strained $60^\circ$ bond angles in the $P_4$ tetrahedron make it thermodynamically and kinetically less stable and highly reactive. Red phosphorus, being polymeric with relieved bond-angle strain, is much less reactive and does not ignite spontaneously in air; it needs to be heated to a much higher temperature to catch fire.

Step 4: Overall. …

Compare white and red phosphorus point by point across structure, physical properties (texture, solubility, toxicity, glow) and chemical stability/reactivity, trac …

• Do not omit the structural root cause (discrete P4 tetrahedra vs polymeric chains of P4 units) — listing only surface properties without this explanation is incomplete. …