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

Ametaller yüksek iyonlaşma enerjilerine sahiptir, bu da değerlik elektronlarının bir atomdan diğerine aktarılmasını zorlaştırır. Bu nedenle, ametaller atomlar arasında değerlik elektronlarını paylaşma eğilimindedir ve kovalent bağlar oluşturur.
Kovalent bağdaki paylaşılan elektron çiftine bağ çifti denir. Bağa katılmayan herhangi bir değerlik elektronuna yalnız çift veya bağ yapmayan elektronlar denir.
Oktet kuralına göre, bazı atomların değerlik kabuklarında sekizden az elektron olduğunda, en yakın soy gazın konfigürasyonunu elde ederek kararlı bileşikler oluşturmak için reaksiyona girerler.
Örneğin, bir amonyak molekülünde nitrojen, en yakın soy gaz konfigürasyonuna ulaşmak için üç elektrona veya bir oktet gerektirirken, hidrojenin en yakın soy gaz konfigürasyonuna veya bir düete ulaşmak için bir elektrona daha ihtiyacı vardır. Böylece nitrojen atomu, üç hidrojen atomu ile tekli bağlar oluşturur.
Öte yandan, karbondioksit ve karbon monoksit molekülleri, sırasıyla karbon-oksijen ikili ve üçlü bağları ile bir arada tutulur. İkili ve üçlü bağların oluşumu, kurucu atomların her birinin en yakın soy gaz konfigürasyonuna ulaşmasını sağlar.
Farklı elementlerin iki atomu arasında kovalent bağlar oluştuğunda, daha elektronegatif atom elektronları daha güçlü bir şekilde çekerek polar bir kovalent bağ oluşturur. Bir atomun elektronları kendine doğru çekme yeteneğine elektronegatiflik denir. Elektronegatiflik farkı ne kadar büyükse, bağ o kadar polar olacaktır.
Pauling ölçeği, bağ enerjisi hesaplamalarına dayalı olarak her bir eleman için elektronegatiflik değerini sağlar. Azot, karbondan daha elektronegatiftir, bu da hidrojenden daha elektronegatiftir.
Bu nedenle, karbon ve nitrojen arasındaki kovalent bir bağda, daha fazla elektronegatif nitrojen, paylaşılan elektronları kendine doğru çekerken, karbon ve hidrojen arasındaki bir bağda, daha elektronegatif karbon, elektron yoğunluğunu daha az elektronegatif hidrojenden uzaklaştırır.

<a href="https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding">Openstax, Chemistry 2e, Section 7.2: Kovalent Bağlar'dan uyarlanmıştır. </a>

polar kovalent bağlar

Her iki atom da elektronları kendilerine çekme konusunda benzer eğilimlere sahip olduğunda (yani her iki atom da aynı veya oldukça benzer iyonlaşma enerjilerine ve elektron ilgilerine sahip olduğunda) iki atom arasında kovalent bağlar oluşur. Ametal atomlar sıklıkla diğer ametal atomlarla kovalent bağlar oluşturur. Örneğin hidrojen molekülü H_2, iki hidrojen atomu arasında kovalent bir bağ içerir. Belirli bir potansiyel enerjiye sahip iki ayrı hidrojen atomu birbirine yaklaştığında değerlik yörüngeleri (1s) üst üste binmeye başlar. Her hidrojen atomundaki tek elektronlar daha sonra her iki atom çekirdeği ile etkileşime girerek her iki atomun etrafındaki alanı kaplar. Paylaşılan her bir elektronun her iki çekirdeğe olan güçlü çekimi sistemi stabilize eder ve bağ mesafesi azaldıkça potansiyel enerji azalır. Atomlar birbirine yaklaşmaya devam ederse iki çekirdekteki pozitif yükler birbirini itmeye başlar ve potansiyel enerji artar. Bağ uzunluğu, en düşük potansiyel enerjinin elde edildiği mesafeye göre belirlenir. Bir bağın apolar veya polar kovalent oluşu, elektronegatiflik adı verilen bağ atomlarının bir özelliği tarafından belirlenir.

Elementlerin elektronegatiflik değerleri yirminci yüzyılın en ünlü kimyagerlerinden biri olan Linus Pauling tarafından ortaya atılmıştır. Elektronegatiflik, bir atomun elektronları (veya elektron yoğunluğunu) kendine çekme eğiliminin bir ölçüsüdür. Elektronegatiflik, paylaşılan elektronların bir bağdaki iki atom arasında nasıl dağıtıldığını belirler. Bir atom bağlarındaki elektronları ne kadar güçlü çekerse, elektronegatifliği de o kadar büyük olur. Bir atomun bir bağdaki elektronları ne kadar sıkı çektiğini açıklar. Ölçülmeyen, hesaplanan boyutsuz bir niceliktir. Pauling, farklı türdeki bağları kırmak için gereken enerji miktarlarını karşılaştırarak ilk elektronegatiflik değerlerini elde etti. Polar bir kovalent bağdaki elektronlar daha elektronegatif olan atoma doğru kayar; bu nedenle, daha elektronegatif olan atom, kısmi negatif yüke sahip olandır. Elektronegatiflik farkı ne kadar büyük olursa, elektron dağılımı o kadar polarize olur ve atomların kısmi yükleri de o kadar büyük olur.

Polar Kovalent Bağlar

Kovalent bağlar, her ikisi de elektronları kendilerine çekmek için benzer eğilimlere sahip olduğunda (yani, her iki atom da aynı veya ...

Education

JoVE Core

Organic Chemistry

Organik Kimya

Unit 1

Ünite 1

Covalent Bonding and Structure

Kovalent Bağlanma ve Yapı

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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.

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Electronegativity in Polar Covalent Bonds

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