Inert Pair Effect - Steric Activity of The Lone Pair

Steric Activity of The Lone Pair

The chemical inertness of the s electrons in the lower oxidation state is not always married to steric inertness, (where steric inertness means that the presence of the s electron lone pair has little or no influence on the geometry of molecule or crystal). A simple example of steric activity is that of SnCl2 which is bent in accordance with VSEPR. Some examples where the lone pair appears to be inactive are bismuth(III) iodide, BiI3, and the BiI3−
6 anion. In both of these the central Bi atom is octahedrally coordinated with little or no distortion, in contravention to VSEPR theory. The steric activity of the lone pair has long been assumed to be due to the orbital having some p character, i.e. the orbital is not spherically symmetric. More recent theoretical work shows that this is not always necessarily the case. For example the litharge structure of PbO contrasts to the more symmetric and simpler rock salt structure of PbS and this has been explained in terms of PbII − anion interactions in PbO leading to an asymmetry in electron density. Similar interactions do not occur in PbS. Another example are some thallium(I) salts where the asymmetry has been ascribed to s electrons on Tl interacting with antibonding orbitals.

Read more about this topic:  Inert Pair Effect

Famous quotes containing the words activity, lone and/or pair:

    You must learn to be still in the midst of activity and to be vibrantly alive in repose.
    Indira Gandhi (1917–1984)

    Your star, steel-set, keeps lone and frigid tryst
    to freighted ships, baffled in wind and blast.
    Hilda Doolittle (1886–1961)

    Oh, Jacques, we’re used to each other, we’re a pair of captive hawks caught in the same cage, and so we’ve grown used to each other. That’s what passes for love at this dim, shadowy end of the Camino Real.
    Tennessee Williams (1914–1983)