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:
“In communist society, where nobody has one exclusive sphere of activity but each can become accomplished in any branch he wishes, society regulates the general production and thus makes it possible for me to do one thing today and another tomorrow, to hunt in the morning, fish in the afternoon, rear cattle in the evening, criticize after dinner, just as I have a mind, without ever becoming hunter, fisherman, shepherd or critic.”
—Karl Marx (18181883)
“In the lowlands I have no comrade, not even the lone mans friend”
—Thomas Hardy (18401928)
“There are two kinds of truth; the truth that lights the way and the truth that warms the heart. The first of these is science, and the second is art.... Without art science would be as useless as a pair of high forceps in the hands of a plumber. Without science art would become a crude mess of folklore and emotional quackery.”
—Raymond Chandler (18881959)