Pseudo-noble-gas core

The metals in Group IIA have two valence electrons, both in an s-subshell outside the stable noble gas core. It should not be surprising that each forms an ion with a 2+ charge, the result of losing both valence electrons. Be2+, Mg2+, and Ca2+ each have the stable electronic configuration of a noble gas. The l[Kr]3d °) configuration of the strontium ion, Srz+, with a completely tilled 3d-subshell outside the [Kr] noble gas core, is called a pseudo-noble gas core. Pseudo-noble gas cores are very stable, too. Don t be confused by this. Focus on the valence electrons, those in the highest occupied principal shell, the n = 5 shell in strontium. They are the chemically important electrons. 

Boron and aluminum have noble-gas cores plus three electrons with the configuration ns np. Gallium has an additional filled 3d subshell. The noble-gas core together with (n 1 )d electrons is often referred to as a pseudo-noble-gas core, because these... 

An electron in an atom outside the noble-gas or pseudo-noble-gas core is called a valence electron. Such electrons are primarily involved in chemical reactions, and similarities among the configurations of valence electrons (the valence-shell configurations) account for similarities of the chemical properties among groups of elements. 

Proton a particle found in the nucleus of the atom it has a positive charge equal in magnitude, but opposite in sign, to that of the electron and a mass 1836 times that of the electron. (2.3) Pseudo-noble-gas core the noble-gas core together with ( - l)[Pg.1119]

A noble gas core with an outer d configuration is known as a pseudo-noble gas configuration. A d cation is stable because the third shell is completely filled with 18 electrons, with 10 electrons in the d sub-shell. 

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