Gas phase ion chemistry is a field of science encompassed within both chemistry and physics. It is the science that studies ions and molecules in the gas phase, most often enabled by some form of mass spectrometry. By far the most important applications for this science is in studying the thermodynamics and kinetics of reactions. For example one application is in studying the thermodynamics of the solvation of ions. Ions with small solvation spheres of 1, 2, 3 . . . solvent molecules can be studied in the gas phase and then extrapolated to bulk solution.