Confinement induced chemical bonding: Case of noble gases

Chemical bonding is a fuzzy concept in chemistry defined based on different models since it is neither an experimentally observable quantity nor there is any Hermitian quantum mechanical operator corresponding to this. This chapter presents some examples to show how confinement can even induce chemical bonding in between two noble gas (Ng) atoms in true sense. The Xe-Xe bond can undoubtedly be assigned as a genuine chemical covalent bond and the Ar-Ar and Kr-Kr bonds have at least some partial covalent character. Depending on the size of cavitand and size of the Ng, the degree of covalent bond formation either between Ng and cage centers or between two Ng atoms gets formed. Confinement of Ng₂ becomes a playground for the application of different bonding models and each model has their own advantages and limitations which further create debate.