Detailed numerical study shows that along certain directions in the parameter space the periodicity of the forced Brusselator appears in the same order as that in one-dimensional nuimodal mappings, i.e. in accordance with the U-sequence of Metropolis, stein and Stein. We find a simple method to assign words from a symbolic dynamics of two letters to periods in the model. Our results show the neccesity to enlarge the parameter space in similar research ia order to have a global picture of the bifurcation and chaos "spectrum".