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The octet rule is a chemical rule of thumb that reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. The rule is especially applicable to carbon, nitrogen, oxygen, and the halogens; although more generally the ...
Different compounds that obey the octet rule (sp-elements) and hydrogen can be placed on the triangle. Unfortunately, d-elements cannot be analysed using van Arkel-Ketelaar triangle, as their electronegativity is so high that it is taken as a constant.
Since these compounds tend to be more reactive than compounds that obey their rule, electron counting is an important tool for identifying the reactivity of molecules. While the counting formalism considers each atom separately, these individual atoms (with their hypothetical assigned charge) do not generally exist as free species .
The formulae of simple oxyanions are determined by the octet rule. The corresponding oxyacid of an oxyanion is the compound H z A x O y. The structures of condensed oxyanions can be rationalized in terms of AO n polyhedral units with sharing of corners or edges between polyhedra.
A trick is to count up valence electrons, then count up the number of electrons needed to complete the octet rule (or with hydrogen just 2 electrons), then take the difference of these two numbers. The answer is the number of electrons that make up the bonds. The rest of the electrons just go to fill all the other atoms' octets.
On these views, he proposed the rule of eight or octet rule: Ions or atoms with a filled layer of eight electrons have a special stability. [17] Moreover, noting that a cube has eight corners Lewis envisioned an atom as having eight sides available for electrons, like the corner of a cube.
Main-group atoms generally obey the octet rule, while transition metals generally obey the 18-electron rule. The noble gases (He, Ne, Ar, Kr, Xe, Rn) are less reactive than other elements because they already have a noble gas configuration. Oganesson is predicted to be more reactive due to relativistic effects for heavy atoms.
[2] [25] Interestingly, the excited state does not obey the octet rule as the carbon atoms have an average 6.5 valence electrons surrounding them. Further, the internuclear region contains only three electrons, the same as in the benzene molecule ( see above ), and this explains why the carbon-carbon bond length in the excited state of ...