Inert pair effect

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Inert pair effect refers to the fact that "valence electrons in an s orbital penetrate to the nucleus better than electrons in p orbitals, and as a result they're more tightly bound to the nucleus and less able to participate in bond formation. A pair of such electrons is called an "inert pair". The inert pair effect explains why common ions of Pb are Pb4+ and Pb2+, and not just Pb4+ as we might expect from the octet rule." [1]

The heuristic device of pretending an electron orbits the nucleus like a planet orbits a star is sometimes used to "explain" this relativistic effect on the shape of a molecule's electron which is the three dimensional shape of its potential for interacting (due to its energy level) called a molecular orbital. This is at the expense of correctly understanding both the quantized and wave-particle duality aspects of fundamental particles.

The inert pair effect is apparent from the chemistry of the Group III and Group IV elements and beyond. The lighter elements in Group IV tend to have a valency of +4, whereas the heavier elements form 2+ ions that are more stable than 4+ ions. For instance, PbO is much more stable than PbO₂ which decomposes readily to PbO.

The inert pair effect can be used to make predictions concerning the properties of elements; for instance, although roentgenium has never been seen by the naked eye, the inert pair effect suggests that it should be colored like gold.

External links

• Chemistry guide A good explanation.de:Relativistischer Effekt