Phosphorus Oxides

P₄O₆ (oxidation state of P is +3) and P₄O₁₀ (oxidation state of P is +5) are known: they both have tetrahedral cage structures, the difference being that the terminal cage positions are occupied in P₄O₁₀ whereas they are not in P₄O₆.

P4O6: terminal positions of tetrahedron unoccupied		P4O10: terminal positions of tetrahedron occupied

P₄O₆ is formed when phosphorus is burnt in an insufficient supply of oxygen.

The oxides of P both react with water to give acids, P₄O₆ giving phosphorous acid H₃PO₂, and P₄O₁₀ giving phosphoric acid H₃PO₄. The rapid reaction of P₄O₁₀ with water means that it is often used as a drying agent.

Arsenic, Antimony and Bismuth Oxides

As₄O₆ has the same structure as P₄O₆, and As₄O₁₀ decays rapidly on heating to give As₄O₆ and oxygen.

Sb₄O₆ consists of molecules with the P₄O₆ structure in the gas and solid phases.

Bi only forms a stable oxide in the +3 oxidation state (Bi₂O₃). The Bi^VI oxide is very unstable.