Inert pair effect and its relationship with chemical periodicity
Abstract
In the 1, 2, and 13-18 main-group elements, the general trends in atomic properties such as size (r radius), electronegativity (c), ionization potential (In), and electron affinity (Ae) that are used to identify the bond type, as well as the chemical reactivity of elements, are explained by three aspects: the nuclear effective charge Z*, electron-electron repulsions, and the stability of the valence shell. These trends are known as chemical periodicity and, for lighter elements, their generalization is valid. However, for heavy p-block elements there are periodicity anomalies attributed to a relativistic effect known as inert pair. In post-transitional or p-block elements, the inert pair effect explains the formation of stable ions with low oxidation numbers, the unexpected high values of ionization potential, as well as the non-participation of the ns2 orbital (n = 4, 5 and 6) in the chemical bond.
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References
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