Density functional theory is used to study electronic and physical properties of pure Rh-n (n = 1-6) clusters in their ground state and those of their closest states. Optimized equilibrium bond lengths and angles, absolute and binding energies, charge distributions, and Mulliken populations are determined. The clusters chemistry is tested via adsorption of atomic oxygen and hydrogen, where a systematic study of the preferred adsorbate adsorption site is performed. Bridge sites are the preferred ones in most cases for oxygen adsorption in small rhodium clusters. The case of hydrogen is less conclusive; the small size of the adsorbate may favor top or bridge sites depending on the metal cluster morphology. Details of the interactions of metal cluster-adsorbate are analyzed via the distribution of electronic population and charge transfer.