Ionic liquids are used for many applications such as electrolytes for energy storage in electric double-layer capacitors and dye-sensitized solar cells for conversion of solar energy. The nonextensivity of entropy was investigated for different sizes of colloidal Ag nanoparticles (NPs) and it was shown that subextensivity of entropy occurs for colloidal Ag NPs. In small size of colloidal Ag NPs and at low temperature, nonextensivity is important. The pattern of configurational entropy for Ag NPs in terms of size in gas phase is completely different with colloidal Ag NPs in [EMim][PF6] ionic liquid as a solvent. Configurational entropy of colloidal silver NPs in terms of size of colloidal Ag NPs is nonmonotonic. There is a nonmonotonic behavior for mean collision time of vibrational mode of colloidal Ag NP size in IL; however, mean collision time of vibrational mode for Ag NP in gas phase decreases monotonically as the Ag NP size increases. The increase of the size of colloidal silver NP does not change [EMim] cation configuration around colloidal silver NP.