Binary ionic compounds Lewis structures

We have already seen that when metals and nonmetals react to form solid binary ionic compounds, electrons are transferred and the resulting ions typically have noble gas electron configurations. An example is the formation of KBr, where the K ion has the [Ar] electron configuration and the Br- ion has the [Kr] electron configuration. In writing Lewis structures, the rule is that... 

The binary compounds of carbon with metals, metalloids, and certain nonmetals are called carbides. The more active metals form ionic carbides, and the most common of these contain the acetylide ion (C2 ). This ion is isoelectronic with N2, and its Lewis structure, [ C=C ], has a carbon-carbon triple bond. The most important ionic carbide is calcium carbide (CaC2), produced by the reduction of CaO with carbon at high temperature ... 

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