Name: covalent bond overlap and orbital hybridization
Uploaded: 2025-05-22T09:05:33.000Z
Duration: 2 min 38 s
Channel: JoVE

Die Valenzbindungstheorie geht davon aus, dass eine chemische Bindung durch eine Überlappung von teilweise gefüllten Atomorbitalen entsteht, einschließlich solcher, die nicht das sphärische s-Orbital sind.
Wenn sich eine einzelne Bindung zwischen zwei nicht-sphärischen Orbitalen bildet, überlappen sich die beiden Orbitale Kopf-an-Kopf.
Die Art der kovalenten Bindung, die durch Kopf-an-Kopf-Überlappung von Atomorbitalen gebildet wird, wird als Sigma-Bindung bezeichnet.
s- und p-Orbitale, die sich überlappen, um kovalente Bindungen zu bilden, können die verschiedenen Molekülformen im VSEPR-Modell nicht ergeben. Die Valenzbindungstheorie hilft, diese molekulare Geometrie durch die Hybridisierung oder Vermischung von Atomorbitalen zu erklären.
Einige Atomorbitale, die an der Bindung beteiligt sind, rekombinieren sich zu neuen Orbitalen, deren Formen eine Mischung aus den Originalen sind. Die anfängliche Anzahl der erzeugten Atomorbitale und die Anzahl der erzeugten Hybridorbitale ist immer gleich.
Die Hybridorbitale haben eine andere Form als ihre konstituierenden Atomorbitale, wobei ein Lappen deutlich größer ist als der andere. Somit ist die Wahrscheinlichkeitsdichte des Elektrons in einem Richtungslappen stark konzentriert, was zu einer effektiveren Überlappung mit den Orbitalen anderer Atome führt. Der Übersichtlichkeit halber sind diese Orbitale oft ohne die kleinen Lappen dargestellt.
Im angeregten Zustand von Kohlenstoff werden beispielsweise die Orbitale von einem s und drei p, die die vier ungepaarten Elektronen enthalten, hybridisiert, wodurch vier äquivalente hybride s-p-three-Orbitale entstehen, die die Eckpunkte eines regulären Tetraeders einnehmen.
Das Mischen von einem s- und zwei p-Orbitalen im angeregten Zustand von Kohlenstoff erzeugt drei äquivalente s-p-two-Hybridorbitale mit trigonaler planarer Geometrie.
In ähnlicher Weise kann die Hybridisierung eines s- und eines p-Orbitals zwei sp-Orbitale erzeugen, die um 180 Grad zueinander ausgerichtet sind. 
Das Konzept der Hybridisierung liefert auch eine Erklärung für die Bildung von Mehrfachbindungen. Durch die seitliche Überlappung zweier p-Orbitale entsteht eine pi-Bindung.
Eine Pi-Bindung kann jedoch nur in Doppel- und Dreifachbindungen gebildet werden, wenn bereits eine Sigma-Bindung zwischen zwei Atomen besteht. Da die Pi-Bindung auf gegenüberliegenden Seiten der Kernachse existiert, können sich Pi-Bindungen nicht um diese Achse drehen.

valenzbindungstheorie und hybridisierte orbitale

Valence Bond Theory and Hybridized Orbitals

Gemäß der Valenzbindungstheorie entsteht eine kovalente Bindung, wenn: (1) ein Orbital eines Atoms ein Orbital eines zweiten Atoms überlappt und (2) sich die einzelnen Elektronen in jedem Orbital zu einem Elektronenpaar verbinden. Die Stärke einer kovalenten Bindung hängt vom Ausmaß der Überlappung der beteiligten Orbitale ab. Eine maximale Überlappung ist möglich, wenn sich die Orbitale auf einer direkten Linie zwischen den beiden Kernen überlappen.

Eine σ-Bindung (Einzelbindung in einer Lewis-Struktur) ist eine kovalente Bindung, bei der die Elektronendichte im Bereich entlang der Kernachse konzentriert ist. Eine π-Bindung ist eine kovalente Bindung, die durch die nebeneinanderliegende Überlappung zweier p-Orbitale entsteht. In einer π-Bindung liegen die Bereiche der Orbitalüberlappung auf gegenüberliegenden Seiten der Kernachse, während sich entlang der Achse ein Knoten (eine Ebene ohne Wahrscheinlichkeit ein Elektron zu finden) befindet. Alle Einfachbindungen sind σ-Bindungen, während Mehrfachbindungen sowohl aus σ- als auch aus π-Bindungen bestehen.

Wenn Atome in einem Molekül miteinander verbunden sind, können die Wellenfunktionen für Atomorbitale kombiniert werden, um neue mathematische Beschreibungen mit unterschiedlichen Formen zu erzeugen. Dieser Vorgang wird Hybridisierung genannt und wird mathematisch durch die lineare Kombination von Atomorbitalen erreicht. Die resultierenden neuen Orbitale werden Hybridorbitale genannt.

Die Formen und Orientierungen von Hybridorbitalen, die nur in kovalent gebundenen Atomen gebildet werden, unterscheiden sich von denen von Atomorbitalen in isolierten Atomen. Die Anzahl der Hybridorbitale ist gleich der Anzahl der Atomorbitale, die zu ihrer Erzeugung kombiniert wurden. Alle Orbitale in einer Reihe von Hybridorbitalen sind in Form und Energie gleich und ihre Ausrichtung wird durch die VSEPR-Theorie vorhergesagt. Hybridorbitale überlappen sich, um σ-Bindungen zu bilden, während sich nichthybridisierte Orbitale überlappen, um π-Bindungen zu bilden.

Im angeregten Zustand von Kohlenstoff beispielsweise hybridisieren das eine 2s- und die drei 2p-Orbitale, wodurch vier entartete Hybrid-sp3-Orbitale entstehen, die tetraedrisch ausgerichtet sind. In einem Methanmolekül überlappt das 1s-Orbital jedes der vier Wasserstoffatome mit einem der vier sp3-Orbitale des Kohlenstoffatoms und bildet so eine Sigma-Bindung (σ).

In ähnlicher Weise erzeugt die Mischung von einem 2s-Orbital und zwei der 2p-Orbitale des Kohlenstoffs drei äquivalente sp2-Hybridorbitale mit trigonaler planarer Geometrie, während die Hybridisierung eines 2s- und eines der 2p-Orbitale zwei sp-Orbitale erzeugt, die im 180°-Winkel zueinander ausgerichtet sind.

Für Atome, die d-Orbitale in ihren Valenzunterschalen haben, ergibt die Hybridisierung von fünf Valenzschalen-Atomorbitalen (eines s, drei p und eines der d-Orbitale) fünf sp3d-Hybridorbitale mit trigonaler bipyramidaler Geometrie. Eine oktaedrische Anordnung von sechs Hybridorbitalen wird durch Mischen von sechs Valenzschalen-Atomorbitalen (eines s-, drei p- und zwei der d-Orbitale) erhalten, was sechs sp3d-Hybridorbitale ergibt.

Dieser Text wurde angepasst von<a href="https://openstax.org/books/chemistry-2e/pages/8-1-valence-bond-theory">Openstax, Chemistry 2e, Abschnitt 8.1 Valence Bond Theory</a> und <a href="https://openstax.org/books/chemistry-2e/pages/8-2-hybrid-atomic-orbitals">Abschnitt 8.2 Hybrid Atomic Orbitals</a>.

Valenzbindungstheorie und hybridisierte Orbitale

Nach der Valenzbindungstheorie entsteht eine kovalente Bindung, wenn: (1) ein Orbital auf einem Atom ein Orbital auf einem zweiten Atom überlappt und (2) das einzelne ...

valence-bond-theory-and-hybridized-orbitals

Education

Lehre

JoVE Core

Organic Chemistry

Organische Chemie

Unit 1

Einheit 1

Covalent Bonding and Structure

Kovalente Bindung und Struktur

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

covalent bond overlap and orbital hybridization

Covalent bonds form when orbitals on two atoms overlap and their single electrons pair up. The bond is stronger when the overlap is greater. Maximum overlap happens when the orbitals meet along a direct line between the two nuclei.

A sigma bond, or σ bond, is the kind of covalent bond found in a single bond in a Lewis structure. In a σ bond, electron density is concentrated along the internuclear axis. A pi bond, or π bond, forms when two p orbitals overlap side by side. In a π bond, the overlap lies on opposite sides of the internuclear axis, and a node with no electron probability lies along the axis. Single bonds are σ bonds, while multiple bonds include both σ and π bonds.

When atoms join in a molecule, atomic orbital wave functions can combine to make new orbital shapes. This process is called hybridization, and it is described by the linear combination of atomic orbitals. The new orbitals are called hybrid orbitals. They form only in covalently bonded atoms, and their shapes and orientations differ from those of atomic orbitals in isolated atoms. The number of hybrid orbitals matches the number of atomic orbitals used to make them. Orbitals in one hybrid set have the same shape and energy, and their directions follow VSEPR theory. Hybrid orbitals form σ bonds, while unhybridized orbitals form π bonds.

Carbon shows this pattern clearly. In its excited state, one 2s orbital and three 2p orbitals hybridize to form four equivalent sp3 orbitals arranged tetrahedrally. In methane, each hydrogen 1s orbital overlaps with one carbon sp3 orbital to make a σ bond. One 2s orbital and two 2p orbitals can also mix to make three equivalent sp2 orbitals with trigonal planar geometry. When one 2s orbital mixes with one 2p orbital, two sp orbitals form and point 180° apart.

Atoms with d orbitals in the valence shell can form larger hybrid sets. Mixing five valence shell atomic orbitals, one s, three p, and one d, gives five sp3d hybrid orbitals with trigonal bipyramidal geometry. Mixing six valence shell atomic orbitals, one s, three p, and two d, gives six sp3d2 hybrid orbitals with octahedral geometry.

Covalent Bond Overlap and Orbital Hybridization

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Learn how orbital overlap forms sigma and pi bonds, then see how hybridization creates sp3, sp2, sp, sp3d, and sp3d2 orbitals in molecules.

Covalent Bond Overlap and Orbital Hybridization | JoVE K12

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Covalent Bond Overlap and Orbital Hybridization

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