VA group elements form tri oxides and pentoxides of the type $M_2{O}_3$and  $M_2{O}_5$ respectively (M-VA group element). The trioxides and pentoxides of nitrogen are monomers and that of P,As,Sb are dimmers. Nitrogen forms various oxides ranging from N₂O to $N_2{O}_5.$ Oxides of phosphorous have cage like structures.