The Species Group node () contains information on a molecular level about the volumetric species and the surface species present in the model. The Property for Volumetric Species or Property for Surface Species tables typically collect parameters from when importing CHEMKIN transport files.

This node is automatically added when either the Reversible Reaction Group or the Equilibrium Reaction Group is used.

For the case of temperature dependent reaction kinetics, a Species Thermodynamics subnode is automatically created in which the thermodynamic properties of the species can be specified.