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The second important aspect of self-assembly is the predominant role of weak interactions (e.g. Van der Waals, capillary, , hydrogen bonds, or entropic forces) compared to more "traditional" covalent, ionic, or metallic bonds. These weak interactions are important in materials synthesis for two reasons.
Nitrosyl (NO) binds to metals in one of two extreme geometries - bent where NO is treated as a pseudohalide (NO −), and linear, where NO is treated as NO +.; Dioxygen can be non-innocent, since it exists in two oxidation states, superoxide (O 2 −) and peroxide (O 2 2−).
A mnemonic is a memory aid used to improve long-term memory and make the process of consolidation easier. Many chemistry aspects, rules, names of compounds, sequences of elements, their reactivity, etc., can be easily and efficiently memorized with the help of mnemonics.
A solid with extensive hydrogen bonding will be considered a molecular solid, yet strong hydrogen bonds can have a significant degree of covalent character. As noted above, covalent and ionic bonds form a continuum between shared and transferred electrons; covalent and weak bonds form a continuum between shared and unshared electrons.
Under the framework of valence bond theory, resonance is an extension of the idea that the bonding in a chemical species can be described by a Lewis structure. For many chemical species, a single Lewis structure, consisting of atoms obeying the octet rule, possibly bearing formal charges, and connected by bonds of positive integer order, is sufficient for describing the chemical bonding and ...
A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bonds, or some combination of these effects.
[7] [8] While Lewis supported the viewpoint of expanded octet, invoking s-p-d hybridized orbitals and maintaining 2c–2e bonds between neighboring atoms, Langmuir instead opted for maintaining the octet rule, invoking an ionic basis for bonding in hypervalent compounds (see Hypervalent molecule, valence bond theory diagrams for PF 5 and SF 6). [9]
In contrast to chemical cross-links, physical cross-links are formed by weaker interactions. For example, sodium alginate gels upon exposure to calcium ions, which form ionic bonds that bridge between alginate chains. [5] Polyvinyl alcohol gels upon the addition of borax through hydrogen bonding between boric acid and the polymer's alcohol groups.