Name: electronegativity in polar covalent bonds
Uploaded: 2025-05-22T09:05:32.000Z
Duration: 2 min 24 s
Channel: JoVE

K12 Standards

Arizona Science Standards

High School

Physical Science

HS.P1

HS.P1U1.2

Polar Covalent Bonds

Nichtmetalle haben hohe Ionisationsenergien, was es schwierig macht, Valenzelektronen von einem Atom auf ein anderes zu übertragen. Daher neigen Nichtmetalle dazu, Valenzelektronen zwischen Atomen zu teilen und kovalente Bindungen zu bilden.
Das gemeinsame Elektronenpaar in der kovalenten Bindung wird als Bindungspaar bezeichnet. Alle Valenzelektronen, die nicht an der Bindung beteiligt sind, werden als einsames Paar oder nicht bindende Elektronen bezeichnet.
Nach der Oktettregel reagieren bestimmte Atome, wenn sie weniger als acht Elektronen in ihrer Valenzschale haben, zu stabilen Verbindungen, indem sie die Konfiguration des nächstgelegenen Edelgases erreichen.
In einem Ammoniakmolekül benötigt Stickstoff beispielsweise drei weitere Elektronen, um seine nächstgelegene Edelgaskonfiguration oder ein Oktett zu erreichen, während Wasserstoff ein weiteres Elektron benötigt, um seine nächstgelegene Edelgaskonfiguration oder ein Duett zu erreichen. So bildet das Stickstoffatom Einfachbindungen mit drei Wasserstoffatomen.
Auf der anderen Seite werden die Kohlendioxid- und Kohlenmonoxidmoleküle durch Kohlenstoff-Sauerstoff-Doppel- bzw. Dreifachbindungen zusammengehalten. Die Bildung der Doppel- und Dreifachbindungen stellt sicher, dass jedes der konstituierenden Atome die nächstgelegene Edelgaskonfiguration erreicht.
Wenn sich kovalente Bindungen zwischen zwei Atomen verschiedener Elemente bilden, zieht das elektronegativere Atom die Elektronen stärker an und bildet eine polare kovalente Bindung. Die Fähigkeit eines Atoms, Elektronen zu sich hinzuziehen, wird als Elektronegativität bezeichnet. Je größer der Unterschied in der Elektronegativität ist, desto polarer ist die Bindung.
Die Pauling-Skala liefert den Elektronegativitätswert für jedes Element auf der Grundlage von Bindungsenergieberechnungen. Stickstoff ist elektronegativer als Kohlenstoff, der wiederum elektronegativer ist als Wasserstoff.
So zieht in einer kovalenten Bindung zwischen Kohlenstoff und Stickstoff der elektronegative Stickstoff die gemeinsamen Elektronen stärker zu sich an, während bei einer Bindung zwischen Kohlenstoff und Wasserstoff der elektronegative Kohlenstoff die Elektronendichte vom weniger elektronegativen Wasserstoff weg zieht.

Adaptiert von <a href="https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding">Openstax, Chemie 2e, Abschnitt 7.2: Kovalente Bindungen</a>

polare kovalente bindungen

Kovalente Bindungen werden zwischen zwei Atomen gebildet, wenn beide die gleiche Tendenz haben, Elektronen an sich zu ziehen (d. h. wenn beide Atome identische oder ziemlich ähnliche Ionisierungsenergien und Elektronenaffinitäten haben). Nichtmetallatome bilden häufig kovalente Bindungen mit anderen Nichtmetallatomen. Beispielsweise enthält das Wasserstoffmolekül H_2 eine kovalente Bindung zwischen seinen beiden Wasserstoffatomen. Wenn sich zwei getrennte Wasserstoffatome mit einer bestimmten potenziellen Energie einander nähern, beginnen sich ihre Valenzorbitale (1s) zu überlappen. Die einzelnen Elektronen jedes Wasserstoffatoms interagieren dann mit beiden Atomkernen und nehmen den Raum um beide Atome ein. Die starke Anziehungskraft jedes gemeinsamen Elektrons auf beide Kerne stabilisiert das System und die potenzielle Energie nimmt mit abnehmendem Bindungsabstand ab. Nähern sich die Atome weiter einander an, beginnen sich die positiven Ladungen in den beiden Kernen gegenseitig abzustoßen und die potenzielle Energie steigt. Die Bindungslänge wird durch den Abstand bestimmt, bei dem die niedrigste potenzielle Energie erreicht wird. Ob eine Bindung unpolar oder polar kovalent ist, wird durch eine Eigenschaft der Bindungsatome bestimmt, die Elektronegativität genannt wird.

Die Elektronegativitätswerte der Elemente wurden von einem der berühmtesten Chemiker des 20. Jahrhunderts vorgeschlagen: Linus Pauling. Elektronegativität ist ein Maß für die Tendenz eines Atoms, Elektronen (oder Elektronendichte) anzuziehen. Die Elektronegativität bestimmt, wie die gemeinsamen Elektronen zwischen den beiden Atomen in einer Bindung verteilt sind. Je stärker ein Atom die Elektronen in seinen Bindungen anzieht, desto größer ist seine Elektronegativität. Sie beschreibt, wie stark ein Atom die Elektronen in einer Bindung anzieht. Es handelt sich um eine dimensionslose Größe, die berechnet und nicht gemessen wird. Pauling leitete die ersten Elektronegativitätswerte ab, indem er die Energiemengen verglich, die zum Aufbrechen verschiedener Bindungstypen erforderlich waren. Elektronen in einer polaren kovalenten Bindung werden zum elektronegativeren Atom verschoben; Somit ist das elektronegativere Atom dasjenige mit der teilweise negativen Ladung. Je größer der Unterschied in der Elektronegativität ist, desto polarisierter ist die Elektronenverteilung und desto größer sind die Teilladungen der Atome.

Polare kovalente Bindungen

Kovalente Bindungen werden zwischen zwei Atomen gebildet, wenn beide ähnliche Tendenzen haben, Elektronen an sich anzuziehen (d.h. wenn beide Atome identische oder ...

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

electronegativity in polar covalent bonds

Polar covalent bonds form when atoms share electrons unevenly. This happens in covalent bonds between atoms that have similar, but not identical, tendencies to attract electrons. Nonmetal atoms often make these bonds with other nonmetals. Hydrogen gas, H2, is a simple example of a covalent bond between two hydrogen atoms.

A covalent bond begins when two atoms move close enough for their valence orbitals to overlap. In hydrogen, the 1s orbitals overlap and the single electrons on each atom interact with both nuclei. The shared electrons are attracted to both nuclei, which lowers the potential energy of the system. As the atoms get closer, the bond reaches its length at the point of lowest potential energy.

If the atoms move too close, the positive nuclei begin to repel each other. That repulsion raises the potential energy. The balance between attraction and repulsion sets the bond length. This balance helps explain why covalent bonds are stable at a specific distance.

Whether a covalent bond is polar or nonpolar depends on electronegativity. Electronegativity is an atom’s tendency to attract electron density toward itself. It is a calculated, dimensionless value, not a measured one. Linus Pauling proposed the first electronegativity values by comparing the energy needed to break different bonds.

In a polar covalent bond, the shared electrons shift toward the more electronegative atom. That atom carries the partial negative charge. The other atom carries the partial positive charge. When the electronegativity difference is larger, the bond becomes more polarized and the partial charges become larger.

Electronegativity in Polar Covalent Bonds

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HS.P1U3.4

Electronegativity in Polar Covalent Bonds

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