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{{Short description|Concentration of chemical orbitals on adjacent atoms}}
{{underlinked|date=October 2012}}
In [[chemical bond]]s, an '''Orbitalorbital overlap''' wasis anthe ideaconcentration firstof introduced[[atomic byorbital|orbitals]] on adjacent atoms in the same regions of space. Orbital overlap can lead to bond formation. [[Linus Pauling]] toexplained explainthe importance of orbital overlap in the molecular [[bond angle]]s observed through experimentation; andit is the basis for the concept of [[orbital hybridisationhybridization]]. As ''s''&nbsp;orbitals are spherical (and have no directionality) whileand ''p'' orbitals are oriented 90° to oneeach another.other, Aa theory was needed therefore to explain why molecules such as [[methane]] (CH<sub>4</sub>) had observed bond angles of 109.5°.<ref>Anslyn, Eric V./Dougherty, Dennis A. (2006). ''Modern Physical Organic Chemistry''. University Science Books.</ref> Pauling's theory wasproposed that bondss areand createdp byorbitals on the overlapcarbon ofatom adjacentcan atomiccombine orbitalsto ofform twohybrids atoms.(sp<sup>3</sup> The greaterin the overlapcase of themethane) twowhich orbitals,are thedirected strongertoward the bond.hydrogen atoms. The resultingcarbon bondhybrid isorbitals knownhave asgreater anoverlap [[spwith hybrid]]the andhydrogen itorbitals, exhibitsand strengthcan greatertherefore thanform thatstronger ofC–H an s or p orbitalbonds.<ref>Pauling, Linus. (1960). ''The Nature Of The Chemical Bond''. Cornell University Press.</ref>
 
A quantitative measure of the overlap of two atomic orbitals Ψ<sub>A</sub> and Ψ<sub>B</sub> on atoms A and B is their '''overlap integral''', defined as
'''Orbital overlap''' was an idea first introduced by [[Linus Pauling]] to explain the molecular [[bond angle]]s observed through experimentation and is the basis for the concept of [[orbital hybridisation]]. ''s''&nbsp;orbitals are spherical and have no directionality while ''p'' orbitals are oriented 90° to one another. A theory was needed therefore to explain why molecules such as [[methane]] (CH<sub>4</sub>) had observed bond angles of 109.5°.<ref>Anslyn, Eric V./Dougherty, Dennis A. (2006). ''Modern Physical Organic Chemistry''. University Science Books.</ref> Pauling's theory was that bonds are created by the overlap of adjacent atomic orbitals of two atoms. The greater the overlap of the two orbitals, the stronger the bond. The resulting bond is known as an [[sp hybrid]] and it exhibits strength greater than that of an s or p orbital.<ref>Pauling, Linus. (1960). ''The Nature Of The Chemical Bond''. Cornell University Press.</ref>
 
A quantitative measure of the overlap of two atomic orbitals on atoms A and B is their '''overlap integral''', defined as: <math>\mathbf{S}_\mathrm{AB}=\int \Psi_\mathrm{A}^* \Psi_\mathrm{B} \, dV,</math>

where the integration extends over all space. The star on the first orbital wavefunction indicates the function's [[complex conjugate]] of the function, which in general may be [[complex-valued]].
 
==Overlap matrix==
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:<math>\mathbf{S}_{jk}=\left \langle b_j|b_k \right \rangle=\int \Psi_j^* \Psi_k \, d\tau</math>
 
where
 
:<math>\left |b_j \right \rangle</math> is the ''j''-th basis [[Bra-ket notation|ket]] ([[vector (geometric)|vector]]), and
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:<math>\Psi_j</math> is the ''j''-th [[wavefunction]], defined as :<math>\Psi_j(x)=\left \langle x | b_j \right \rangle</math>.
 
In particular, if the set is normalized (though not necessarily orthogonal) then the diagonal elements will be identically 1 and the magnitude of the [[off-diagonal elementselement]]s less than or equal to one with equality if and only if there is linear dependence in the basis set as per the [[Cauchy–Schwarz inequality]]. Moreover, the matrix is always [[positive-definite matrix|positive definite]]; that is to say, the eigenvalues are all strictly positive.
 
==See also==
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*[[Roothaan equations]]
*[[Hartree–Fock method]]
*[[Pi bond]]
*[[Sigma bond]]
 
==References==
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[[Category:Chemical bonding]]
[[Category:Molecular geometry]]
 
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[[ar:مصفوفة التداخل]]
[[it:Matrice di sovrapposizione]]
[[nl:Orbitaaloverlap]]
[[sv:Överlappsmatris]]
[[zh:重叠矩阵]]
 
 
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