Chemical bond

Approaching atoms experience both attraction and repulsion. Suitable electronic arrangements produce stable structures with characteristic equilibrium separations. The balance creates a lower-energy configuration, while stretching or compressing it changes the energy. Bonding consequently describes geometry together with the energetics of forming and separating chemical structures.

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An ionic model emphasizes electrical attraction between oppositely charged ions. In sodium chloride, ions form an extended crystal rather than separate little sodium-chloride molecules. Its formula records their ratio. Melting, dissolution and electrical conduction depend on the arrangement and mobility of the ions throughout the structure.

References: [1]

Covalent bonding involves shared electronic density and occurs in discrete molecules or extended networks. Sharing need not be equal: different attractions for electrons produce bond polarity. Electronic distribution helps determine molecular geometry, interactions between molecules and the observable behaviour of the resulting substance.

References: [2]

Chemical reactions rearrange connections between atoms. Breaking an existing bond requires energy, while forming new bonds releases it. Overall reaction energetics depend on the combined changes, so energy released during combustion cannot be explained by bond breaking alone without considering the bonds formed in products.

References: [2]