The Types of Bonds in Solids

It is useful to ask what types of bonds characterize solids in general and elemental sohds in particular. In answering this question, it is common to decompose the physical continuum of interactions that hold nature s many and varied soHds together and conclude that there are five ideahzed types of bonding interactions, namely van der Waals, ionic, covalent, metallic, and hydrogen bonding. Let us now consider each briefly in turn. 

Metallic bonding The conceptual idea behind metallic bonding is that the valence electrons are highly delocaHzed, shared among the community of atoms in the solid, and not localized on one particular atom or pair of atoms. In most abstract terms, such metals can thus be perceived as atomic nuclei immersed in a featureless electron glue. Thus, metallic bonds are largely nondirectional, and close-packed structures are mostly adopted. 

1) It is interesting to note that the definition of a van der Waals bond given by The International Union of Pure and Applied Chemistry (lUPAC) is somewhat different to what we use here. Specifically, van der Waals bonds are defined by lUPAC as the attractive or repulsive forces between molecular entities (or between groups within the same molecular entity) other than those due to bond formation or to the electrostatic interaction of ions or of ionic groups with 

2) Helium is left out of this list because its light mass lead it to exhibit special properties due to ensuing strong quantum-mechanical effects/zero-point vibrations. 

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